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FAQ - Oil Heating, Hot water production and plumbing “funnies” in France

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I thought I would try and consolidate some of the queries I have answered on this forum and others, so here it is.

It is a little roughcut, but hey, it's free!

Use it as a guide.

Plumbing funnies

The French use a bewildering variety of piping sizes, materials and techniques. Some of it makes sense, some of it is from tradition, and some of it is borne out of necessity.


The French do not allow the indirect storage of water. That means that neither cold or hot water is stored in open tanks – they are all sealed. The French hot and cold domestic water is supplied all around the house at mains pressure.


Most French plumbing is done in copper. They differ in several ways – the sizes generally range from 10mm (outside diameter or O/D) to 28mm O/D (they do go higher but not in domestic applications).


The 10mm, 22mm and 28mm are identical in size to the UK sizes. However, the French also use 12mm, 14mm, 16mm, 18mm, 20mm sizes.


It is possible to buy 15mm solder ring or end feed fittings (tees, bends, straights, reducers) and pipe in France - see www.cedeo.fr . You can also buy reducers/converters - 15mm to 14mm, 15mm to 16mm and so on. Not very cheap, but available. 






  For comparison, French mains water has a target minimum pressure of 5 bar – the UK is 1 bar. The Hot Water heaters have safety valves (Groupe de Securité) which allow the hot water side pressure to reach 7 bar. The central heating systems are limited to 3 bar.

 (One tip to watch for is that you can often go from one size of copper pipe up or down by simply inserting the smaller pipe into the larger without the need for reducing fittings.)


Malleable iron pipe and fittings are still used in oil-fired central heating systems. It is awkward, heavy, expensive and rather unnecessary….


Plastic PER pipe is catching on as it has in the UK, (where it is known as PEX pipe). The advantages of this pipe are it can be easier to handle, requires no heat to join and is somewhat self-insulating. PER pipe can be run almost like cable. The disadvantages are mostly cost and range. Few Bricos carry a large range of PER fittings such as couplings and tees. In the UK, you have at least 3 well known suppliers of plastic pipe, and availability of pipe and fittings is excellent.









Plastic pipe meets copper pipe. PER/PEX pipe is "Fisher-Price" plumbing, and very good news! 


Note that it is important to avoid long straight runs in 22mm PER/PEX pipe for the simple reason that it expands 10 times more than Copper pipe, and will distort or excessively pressure the ends of the run. PEX pipe typically expands by 1%, copper by 0.1% over a 60 deg temperature rise. In real terms, a 10m run of PEX will "grow" by 100mm or 4". Copper pipe will "grow" by only 10mm. 


The upper 22mm PEX pipe has distorted due to expansion as the system temperature increased.

The lower 22mm PEX pipe is unheated and remains straight.


Oil Heating


French heating oil is red diesel, unlike paraffin in the UK – so UK boilers won’t function without modification or burner replacement.


Oil boilers are supplied with or without burner, and with or without a ballon (a small hot water tank). Condensing oil boilers don’t really exist in France.


Oil boilers need an oil tank – there are two basic types. In steel (not many about in domestic sizes nowadays) or plastic, you can get bunded (double paroi) or non-bunded (simple paroi). If you buy a non-bunded tank, you MUST (by law) place it within a bund wall. The reason for this is that any leakage or spillage MUST be contained, and must NOT be able to contaminate the ground or any water courses or plant life. A bund wall MUST be able to contain the whole content of the tank + 10%. Alternatively, you get a bunded tank, which has 2 skins. Guess what the outer skin is for? There is no requirement for a bund wall with these. They cost about double the price of a non-bunded, or course.


The tank and boiler must be sited at least 1m apart from their nearest points, unless there is a full non-flammable wall between them.


The capacity of the tank depends on usage, physical space and how many times a year you want it filled or not. A small-medium property with 6-12 radiators may get by on 1000 Litres. Any more would probably be too large to site. Make sure Mr. Gazôle can reach it to fill it up…


Tank supplier: http://www.sotralentz.com/uk/habitat/article_detail-11.php


1000L Plastic Fuel Tank


Piping between the tank and the burner is fairly straightforward. It is always done in copper, and 10mm will suffice unless the tank and burner are more than 25m apart. These days, two pipes are used, a flow and a return. The return allows fuel not required by the boiler to return to the tank, and is used to allow easy air bleeding from the fuel supply line. The burner can draw fuel over a reasonable distance and up from about 2-3m below its level. The pipes from the tank enter a filter arrangement, which also has a shut-off tap on it. The filter element will need replacement annually. From the filter, two flexible hoses connect to the burner. This is to allow removal of the burner for boiler servicing without the need to disconnect the oil supply.


Oil filter - filtre de Mazout


Oil boilers must be matched to the burner – you can do this easily by buying a boiler complete with a burner fitted. If you buy a burner separately, make sure the supplier matches it to the boiler in terms of electrical compatibility, mechanical fitment and power output range. In reality, this is quite simple. Most electrical connections are similar, the mechanical aspects are standardised and the power output is a straightforward cross-reference job. It is common to buy a boiler from one manufacturer and a burner from another. It is fairly usual to have to exchange the injector when you buy a new burner. The installation leaflet with the burner will provide a table to allow you to select the right injector size. Invariably, the injector supplied as standard is too large, and would result in the boiler producing full power. Since the final output can be varied by screw adjustment once the burner is operating, it is advisable to select an injector that will provide your nominal output, and still allow you to adjust up or down a few kW. 


Our experience has been disappointing for the consumers. Many of the systems we service have NEVER been set up correctly. They have been fired up and left like that. Properties of modest size have had hideously over-powerful boilers installed, and even then the boiler output has been left at maximum (factory default). The client has been running a seriously inefficient system. This is not in a few case - it is in many cases.


Boiler/Burner from different manufacturers.


The output requirement of the boiler depends on the total load. This is simply the total output of all the radiators added together, plus 10% for losses in the pipe work. It gets complicated when you have to heat a hot tank too. The rule of thumb here is to add 6kW to the load. In practice, this will provide adequate hot water reheating in 90% of cases, and if the hot water is not required, provides additional power to heat the radiators a little quicker.


Therefore, if you have a house with 10 radiators, whose combined output is 22kw, and a hot water tank, your boiler needs to have an output of around 30kW. Since boilers with outputs of 27-32kW are cheap and common, any of these would suffice. It is only then necessary to select the correct injector for the burner (which would probably have an output range of 17-32kW) and have the output set exactly once the system is commissioned.


What if you leave the boiler alone and don’t try and set the output with both the injector or the adjustment? It will probably work, after a fashion. At best you will get a phenomenon that makes the boiler continually fire up and down at regular intervals, which is wasteful on fuel and the burner longevity. At worst you will have a very inefficient, smoky, noisy and possibly dangerous boiler.


Although non-scientific, one can check whether the burner is operating reasonably. Firstly, you should never see smoke from the flue. Steam is fine. Secondly, the burner should always light well, with no flame-outs. Thirdly, there is a little observation window or door or flap that can be opened whilst the burner is running. The flame quality can be observed. In basic terms, the flame should have a distinct orange colour, be a series of flame "licks", not a cloud of flame, and should not have ANY blue or white tips. If the burner flames out on starting, the air needs throttling down. If the flame has blue of white tips or streaks, the air needs throttling down. If the flame is rough and cloudy, the air needs increasing. If there is black smoke from the flue, the air needs increasing. Alternatively, the fuel pressure can be increased or reduced if the air supply needs throttling down or up respectively. I do NOT recommend this course of action. You may run the boiler above its rating....


Burner operation must always be verified and/or adjusted using the correct measuring equipment by an experienced chauffagiste.


Injectors have their nominal oil delivery marked on them – in Gallons per hour. American gallons! You could try to estimate how much fuel you would use per hour/day/month/year…. Injectors should be changed every 2 years (at least) - they wear. Note that Injectors also have their spray pattern marked on them, such as 60S or 45S.  You must use the same spray pattern on any replacements.




All boilers require some form of pipe to exhaust the combustion products. Most oil boilers use 125mm or 150mm aluminised or stainless steel pipe. The pipe begins at the boiler, usually with a type of tee-piece complete with a small drain pipe in the bottom tee to bleed off any condensation that forms into water. The side part of the tee fits onto the boiler, the top part of the tee leads off into the pipe that eventually takes the fumes off through the roof and out. Common exhaust stacks are simply vertical and are made up of 1m lengths fitted into each other for as long as is required. Where directional changes are required, the boiler manual must be consulted to see what is and what isn’t permissible. The manual will also illustrate where the stack outlet can be placed in relation to other buildings and obstacles. These must be heeded.


Pumps and the like.


Firstly, all French central heating systems are sealed systems. There are no expansion tanks. You fill them with water, purge (bleed) all the air out and finally add or subtract some water until the pressure of the cold system is 1.2 -1.5 bar. This should stay like this for months. If it doesn’t, there is a leak of some description. The pressure is read off a small manometer which is part of a safety valve that will allow water to escape if the pressure in the system exceeds 3 bar. This brings me on to another part of a sealed system – the expansion vessel. This is a biggish (red painted) tank that absorbs pressure as the water in the system increases in temperature and thus volume. On the manometer, you see the system pressure rise as the water heats up from typically 1.2 bar to 2 bar. If the pressure rises above 2 bar, the expansion vessel is too small (or requires air pressure adding) and must be exchanged for a larger one. If the pressure rises only a little, who cares? You just have a larger one than you need.


Choosing the right size of expansion vessel depends on 3 variables. 1) The volume of water in the system, 2) the temperature rise of that water, 3) the head of the system (that is, the linear distance between the lowest and the highest point in the system). There are a number of programs on the web for this. The one most trade use (actually on a CD, but online too) is here: http://www.xpair.com/calcul_cardonnel.php?calcul=4


Note that every expansion vessel has a precharge pressure (air pressure!). This is a critical pressure. You may find this on the label of the item; if not, simply use a car tyre type pressure gauge (a good one) on the shrader valve with NO PRESSURE IN THE HEATING SYSTEM - i.e. the manometer reads zero. The pressure should never be below 0.5 bar, and never above 1.5 bar. If the pressure is less than 0.75 bar, you must pump air into the valve until the reading is 1 bar. Otherwise, the vessel cannot function. Also note that the water pressure in the system when cold must be at least 0.2 bar above the precharge pressure. Otherwise the vessel will not function. Since it is preferrable to run the system at no more than 2 bar when hot, it is permissable to reduce the precharge pressure, if it is higher than 1 bar, to 1 bar and fill the system so that the resulting pressure is 1.2 bar. If you follow...!


Water is added to the system via a one-way (non-return) valve, usually near the manometer. Note that only a temporary connection between the one-way valve and the mains is permitted by law. This is to ensure that the mucky water flowing in the radiators cannot enter the mains supply. 


Automatic air-vents should be fitted at strategic points in the system. As a minimum, the highest point in the flow circuit and the flow to the hot tank, if fitted, should have one each. Always fit as high as possible, and always in the flow pipe after pumps and zone valves. Never fit one in the return circuit, or you will draw air INTO the system!


3 Zone valves wth Auto Airvents after


To circulate heated water around the radiators and/or the hot water tank coil requires some form of pump (or more correctly, circulator). The “size” of this depends on several factors, as usual. One of the easy ways of dealing with this is to use a self-regulating pump. These can be set to vary their flow rate depending on the load, automatically. These are superbly suited to systems where the flow rate varies when thermostatic radiator valves (TRVs) open and close, and where a hot water tank will require heat. Highly recommended.


Pump, Expansion vessel, one-way fill valve and Manometer/Relief valve (hose is temporary for flushing)


For some reason, the French insist on fitting something called a “vannes melangeuse” after the pump. This oddity is totally unnecessary and is used to inefficiently control the radiator temperature by allowing some of the boiler flow to immediately return to the boiler – a kind of crude bypass. Never fit one.


To correctly control the “temperature” of the radiators (and thus the heat output into the room) requires the use of TRVs and the correct temperature of the boiler flow to be set. It is normal for at least one radiator NOT to have a TRV fitted – usually a heated towel rail or a bathroom radiator. This is to allow some circulation in case all the TRVs close down. Again, the strong recommendation is to fit an automatic pump, so this becomes academic.


A Room Thermostat could be fitted, but room stats and TRVs in the same room can conflict in terms of conveying comfort all over the house. If a TRV was to close down before the room reached the set temperature of the room stat, the room stat would never open. The boiler would continue ad infinitum. And the converse is true.


To allow the boiler to heat hot water (assuming the hot tank is not an integral part of the boiler), requires a means of allowing boiler flow to circulate in a coil within the tank. This can be achieved in several ways, the most sensible is to use a 2 port zone valve connected to the flow pipe of the heating circuit. The other side of the tank coil goes to the return of the heating circuit. The zone valve is normally closed (by a spring). The tank will have a thermostat on it that is used to energise the zone valve and open it. Zone valves have a switch inside them that closes once the valve is fully open. This is used to switch on the pump and boiler. This can therefore operate independently of the heating circuit if necessary.


Timers or Programmers should be used to allow the heating and hot water, if fitted, to be controlled effectively and efficiently. These are cheap (but not in France) and easy to fit. They are worth it, and I would recommend a two channel one that can control the heating and hot water independently. A frost thermostat, sited correctly, is also peace of mind in spades. I would strongly suggest you buy/specify a Frost stat that has a minimum setting of 0 degrees or less, since you will find the 3 degree up ones come on far too keenly, and your fuel bill will go into orbit. 




All pipework in exposed spaces (roof spaces, greniers, sheds, garages, sous-sols, behind placo walls etc.) must be 100% insulated. The easiest way is to use the grey foam type available in all sorts of sizes.




Once the system is in good order, it must be filled with a Corrosion Inhibitor, and for peace of mind (particularly if your pipe insulation is "variable") Anti-Gel. Or your Assurance may be invalidated.


Note that you can get inhibitor and anti-freeze (anti-gel) in one product. Sentinel X500 is good, http://www.gewater.com/applications/sentinel/x500.jsp or Fernox Alphi 11 http://www.fernox.com/?cccpage=alphi_11&sub=8


With all the above, it is often cheaper to buy in the UK - about half of the price.


Hot Water


There are a couple of options here, assuming your oil boiler doesn’t have a hot tank fitted integrally. The classic means of heating between 100 and 300 Litres of water is to use a Chauffe-Eau or Ballon. These operate on electricity only, and are used on “Heures Creuses” during the night which is French EDF cheap rate. They are efficient and easy to fit – the connections and pipe work come as part of a kit. These, like all hot water production in France, provide hot water at mains pressure. Normally they take about 6 hours to heat a full tank of cold water to 65ºC. They have 1.8-2.4 kW elements, and always buy one with a Steatite element shroud as a minimum. You can get ones with a sacrificial anode and control box which controls the slow corrosion within. They are very dear, require the anode to be changed regularly, and frankly aren’t worth it. And no-one changes the anode, so someone utterly wasted their money.


The next method is to use a similar tank which has a coil inside that connects to the heating circuit, as described above. These are known as Ballon Rechauffages. They can take as little as 30 minutes to heat 200 Litres of cold water to 65ºC.


Better still, you can have a Ballon Rechauffage Mixte, which combines both an electric element (as back-up or for summer use) and a heating coil.


Note that whichever Ballon you choose, once full of water will be very heavy. For instance, a 200 Litre Chauffe-Eau weighs about 50kg empty, and once full will weigh 250kg (¼ Tonne – 1 Litre of water = 1kg). So, mount it somewhere safely and securely, and do use the floor mount system.


Electric Showers


Not very commonplace in France, although they can be bought from Bricos and Merchants. There are a number of reasons for this. In order to get a reasonable shower, a reasonable flow of water at about 38 deg C is required. An 8kW electric shower will deliver a fairly poor flow at this temperature. 8kW is also almost the entire power supply available to the majority of homes (9kW). The French are used to having mains pressure water at whatever temperature they like from their Chauffe-Eaux....etc.etc.


From elsewhere:


Plumbing tips:


  • Even the tiniest speck of dirt is enough to prevent a soldered joint from taking hold. This sounds like plumbers' propaganda, but it's really true.

  • If a solder joint doesn't take hold in a few seconds, it won't take hold in a few minutes either.

  • Even the meagrest trickle of running water along the area to be soldered will prevent the joint taking.

  • No heat-resistant cloth is effective enough to prevent you scorching the floor and walls if it takes you ten minutes to solder the joint.

  • Soldered joints stay hot for a long time afterwards.

  • Burned fingers stay burned for a long time afterwards.

  • If a new joint feels damp when water is re-admitted to the system, if may just be condensation and not a leak. But don't push your luck.

  • It's easier to move a radiator than to build furniture around it.

  • For water plumbing, there are few good reasons to persist in the use of copper pipe and soldered joints. Plastic pipe and push-fit joints are trivial to assemble, at least as reliable, and can be dismantled if necessary.

  • All pipework expands when it warms up. Plastic pipework expands rather more than copper, so needs a bit of extra space at the ends.

  • Plastic pipework is unlikely to burst if the water in it freezes.

(Thanks Kevin Boone)

Opel Fruit, Dept. 53

Dogs have owners, cats have staff.

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<< However, the French also use 12mm, 14mm, 16mm, 18mm, 20mm sizes. Wall thicknesses (of both UK and French copper pipe) vary depending on application and size. The French pipe is generally, size for size, thicker walled than the UK pipe. >>


For the sizes quoted above the external diameter is + 2mm, and hence wall thickness is 1 mm, more than the internal diameter, which means that for instance 12 mm internal diameter pipe will sleeve inside 14 mm.


I have no axe to grind but would point out that a Chevy V8 has half the parts of a Mini 850 engine and can be stripped or reassembled  with two spanner sizes in a quarter of the time.


Provided you buy the right tools, in particular the clamp to restore maleable Frecnh pipe to round before jointing I have no problem French pipework and found it no better or worse than the UK norms

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About five years ago I walked into the local 'briconaughts' with a guy. We spent ten minutes telling the assistant at the quinquilery desk what we wanted. The owner, who I had known for five years, eventually came over and said it was the first time he had ever heard anybody English ask for exactly what they wanted.  A then had to waste ten minutes of my life explaining that 'Anglais' was the French for 'British'  and that my friend was from Edinburgh.    
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In addition, if you elect to have Heures Creuses:

Cool people when rewiring add a "Creuse Bus" to their properties - designated sockets/outlets that are controlled by a jour/nuit contactor. Only when Creuse is active do these sockets (and thus those items around the place you want on Creuse) become live.

Easy to do when you're doing the old place up, and cheap.

Great for Washing machines, pool pumps, Washer Dryers, Dishwashers, Arc Welders.....

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Great for Washing machines, pool pumps, Washer Dryers, Dishwashers, Arc Welders.....

Insomniac Welders, that is. Some folks seem to get HC during the day. We don't.

Excellent info. But, can anyone explain my CH system? Oil fired but not pressurised and without a header. We simply put in water until it comes out of the top (literally). As the system introduces water at the bottom and the rads are fed diagonally, nothing needs bleeding (which is evidenced by the fact that most of the rads do not have a bleed point). Is this normal? And why does it work? Why does the pump not push water out of the top?


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[quote]Ok, you add water where (and how) and top it up until it comes out where?[/quote]

Here goes!

Where - at the bottom of the system (approx level with the bottom boiler connection)

How - turn tap (connected to mains)

Water comes out of a pipe about 50cm above the topmost pipework of the system (it is just te'ed into the return pipe to the boiler), onto the garage roof, as it happens...

Make sense?



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It is a pseudo-sealed system. It isn't really sealed, obviously. I have seen something like this in a recent replacement - the owner had the system unsealed due to a leak they could never find, allegedly. (It was under the screed in the end, watering his foundations).

I suspect the pump is set to a slow speed, and do you have a vannes melange? If so, I suspect it is almost fully set to closed.

The fact that the pipe forming the overflow is in the return pipe means to me that the little circulation there is isn't pulling much air in, so the column of water in the high pipe is just about staying in the pipe. Should you increase the flow rate, by means of the pump speed and/or the opening of the mixer valve, the water in the higher pipe will get drawn into the system and air will follow.

Do you find that the system takes an age to warm the rads? Does the boiler cut in and out frequently?

One of the prerequisites of any system is to ensure that corrosion is controlled. This reduces the rate of corrosion caused by air, water, and the various ferrous and non-ferrous metals present. This is normally done by adding an inhibitor to the system. Sealed or not. Clearly, if you are having to top up any system regularly (more frequently than every 3-6 months), then the inhibitor is going to get diluted and thus increasingly ineffective.

And are you happy with the system? By the way!

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If truth be known, I am not that happy with the system. It doesn't really get the rads that warm, but the house is rather drafty, so it is difficult to tell where the shortcomings really lie! (& yes, I know I must fix the other issues first..).

I believe that the system was installed in 1983. I replaced the burner 6 months ago.

We only have to "open the tap" once per season & that is mainly becuase we think we ought to - it doesn't take much to pour out of the top.

The boiler doesn't cut in and out. It runs for about 20 mins & then stops for an hour or whatever (the boiler 'stat is set for 65deg - is this OK?). Pump (which I replaced 18 months ago) is set to minimum.

I suppose I am steeling myself to replace all the pipework & the rather inefficient rads, in copper, rather than the iron pipe that is currently used. Any reason why I should not simply replace the pipe runs & rads?

No mixer valve BTW.



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I think replacing the rads and pipework would be an excellent idea, and add an expansion vessel and security valve/manometer at the same time to make the system sealed. These are dirt cheap - if you want to pipe them yourself, then an 18L expansion vessel will cost about 15EUR, and the valve/manometer about 7 EUR. Better still, buy the ready piped and bracketed one from Leroy Merlin for about 30 EUR, and just screw a vessel on. It's quick and simple.

I would keep the pipe sizes at 22mm for distribution and tee off to 16mm around the rads. Try and get from iron to copper pipe as soon as you can after the pump and make the pipework simple. The French use top flow, bottom outlet on the rads. Personally, I would stick to Bottom/Bottom. There is no performance difference worth speaking of.

Rads, assuming you want conventional steel jobbies, are cheapest at merchants (although I have just bought 17 off from Leroy Merlin for less than 600 EUR in 4 sizes, all K2s (double panel convector). They are a piece of **** to mount).

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Very interesting and useful. Many thanks.

A couple of questions:

Central Heating. Is Furnox (or equivalent) used/common/rare in France and if so how (and where) does one add it to the system ?

How strict are the regulations re: open flues. My flue does not comply with “norms” and I’m trying to get somebody to change it (exits below roof ridge without 8m clear all round horizontally) – usual “issues” getting any artisan to actually quote/do the work. I thought that if flue is longer than 3m then max deflection from vertical is 20 degrees. However, local plumber is quite happy to deflect to 45 degrees (local plumber is pretty good and not a “bodger”). Should I just go with what he says (as he’s the expert) or try to find a max 20 degree deflection route for him to re-install to (flues are not something I would do myself).


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Anti-corrosion protection: Use Sentinel X100 (£15/1L) or Fernox MB1 (£20/4L) from the UK or look for something like GEB "Protecteur Multimetaux" (€ 25/1L) here in France.

You add them by draining off the system partly (we're talking sealed system?) and removing a rad bleed valve (the whole thing) on a high rad that is empty or part empty and funneling the inhibitor in somehow. Obviously if you have another access point that is easier, use that. Then refill to 1 bar, bleed, top back up to 1 bar and Robert is definitely related to your father.

Bear in mind that you should flush your system (new install or old), before adding Inhibitor, and make sure you don't have any leaks - or the stuff just comes out!

The French SHOULD use inhibitor, but just as the UK heating control operatives SHOULD, they rarely do. Which is why 90% of heating systems in the UK are sludged to death.

Flue: I wouldn't be overly worried about a couple of 45 degree bends. I would if there were 90 degree bends. I would get him to install it with a written Warranty, and also to verify (by measurement) the burner after installation. For peace of mind.

Joining copper to iron: various ways... depends whether you have a thread to screw a fitting onto. Assuming you have, you should find a suitable 40/49 (1 1/2") or 33/42 (1 1/4") (you seem to have something in between, though I doubt it) brass or iron fitting to screw on and reduce to 20/27 (22mm pipe) or 26/34 (28mm pipe). You may have to do it in two fittings if you to 22mm, but maybe not. Best thing is to seek in the Bricos - those that have fittings like this, like Tout Faire.

If you don't have a thread, the practical options are to either braze fittings on, or to ask a local plombier to come and cut you a thread. They charge (literally) beer money for this.

Bund walls: not sure when the requirement became law here, but I suspect a long while ago. If you have a block wall there, it is straightforward enough to seal it with one of the rubberised or epoxy based products, IMHO.

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Hi Opel Fruit, many thanks for the info you posted, who says there's no such thing as a free lunch.

I have talked to my french plumber re building a DIY solar hot water system which he connects to the hot water tank. He says no can do because the system is sealed and pressurised. As we run a chambre d'hotes most of my hot water is needed in the summer months, so if I could use solar to heat the water and somehow get it into the system it would save me a great deal of dosh. Is there a solution to this connection problem?

 Lastly what are your views on the most cost efficient method of heating water, with EDF's help given that demand occurs mornings and late afternoon.

Thanks Wilko:

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There are numerous options. You can get tanks (ballons) from 150L to 300L that just have an electric element and a coil that connects to a solar panel circuit. The advantage of these is that you can heat water "free" during sunny days, and top-up at night for the morning shower on Heures Creuses. You can get solar circuits as kits with the ballon (200L) for around 2000 Eur working on gravity (you need to site the ballon and panels in a manner that encourages good thermosyphon action) or a pumped version (allowing you to site the ballon and panels just about anywhere and any distance apart) for about 500 Eur more. You can get single solar panels (collectors) or double panels for speedier reheating. South of the Loire, 2 panels on a pumped solar system and a 300L ballon will reach 65C in a few hours of sunshine easily. A single panel may just about heat the ballon in a full day.

Another consideration is the siting of the panels. They should be mounted at about 45 degrees from the horizontal, and face south or south west.

Other ballon options include those with two coils inside, one for the solar circuit, and one for a boiler circuit. And you can get ballons with both of the above and an electric element.

I have noticed that there are several specialist suppliers around. For simplicity, I would also try the likes of Leroy Merlin, who have complete ready to fit kits available.

I also notice that solar hot water systems FITTED are ridiculously expensive. I reckon that a competant DIYer could fit the kit (except perhaps the solar panels on high/difficult roofing) within a weekend, particularly if you site the new ballon where one already exists, and a 300L system would cost under 3000 Eur.

(500L twin coil systems are also available.)

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Thank you very much you have given a lot of time to do this post and it has answered a lot of questions for me and I imagine a lot of folkm this is what a forum should be about and I only hope I could help someone in the future as you have done cheers RIK
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Hi I found the advice very helpful I am in the process of having wood burning Villager AHL fire with fitted boiler delivered from the Uk to my holiday home in Laserade Gers . I note that you say that in France they do not have open water tank and everything is sealed . I just want to run a central heating system (6 rads 1 heated towel) I have an efficient water heating system so they will not be linked Do you have any advice on the above . The manual has an open expansion tank shown in the fitting. Are there any good plumbers merchants in my locality Please help
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