Water Pump pressure query

[Gyn_Paul]

This is a question of pressure…

I have one of those pumps which comprises an electric motor with a pump on the end, sitting on top of a red tank. The tank is 20L, horizontally mounted, end fed by a pipe from the pump. The flow is controlled by a pressure switch which opens and closes @ +- 3/3.5 bar. It has worked fine for about 2 years, but recently – although working OK at full bore, it has taken to ‘short-cycling’ when the draw off is restricted (like a refilling toilet tank for example). I’ve emptied and dismantled the tank part and discover that the 5” multi-bolted faceplate hold a rubber liner or bladder in place. At the other end of the tank is a standard schroder tyre valve, so I guess the water flows into the tank and expands the liner against the trapped volume of air.

The question is, when I reassemble it again, what pressure do I pump into it? Is it about 1.5 bar like a CH balon? But then again, the pressure of a CH system doesn’t vary quite as much as this one…

I’m kind of hoping that the dismantling exercise was unnessessary, and that all I needed to do was top up the air pressure, but I always like to know how things work (even if I do routinely end up with 2 tiny screws and a washer left over), and anyway, I cleaned out a whole heap of rust from the back of the face plate, so it wasn’t entirely in vein !

[Chancer]

Good man!

I would have taken it apart as well, even if it had not played up[:)]

Why dont you just keep adding a little bit more pressure each time until it behaves how you want it to?

[Gyn_Paul]

That's the plan in lieu of expert input !

p

[Gluestick]

Standard pumps reservoirs are circa 1.5 Bar.

The fault you described is normally associated to the reservoir pressure being too low.

For the record me too JR!

I've been taking everything apart and putting it back together since I was about five!

I soon learned to identify where and how bits fitted back: and the little trick of a number of spare containers to put stuff into!

Like small screws: you know, the ones that always drop onto the floor and roll miles after they bounced!

The first complex transaxle was fun: with springs balls and plungers from the detents bouncing all around the place......................

[:D]

[Chancer]

At the age of about 5 my father tired of me forever liberating his tools to play with, bought me for christmas a toy like multi-tool with a plastic handle, a couple of screwdriver and gimlet bits and one tiny hammer bit also which fitted in the end but was only good for breaking toffee.

He soon realised that it was a mistake when virtually everything in the house seemed to break down simultaneously due to the lack of some small but vitally important internal part.

I also used my "toolkit" to great advantage as a negotiating tool, if for instance I was sent to my bedroom for being naughty I would creep downstairs unscrew the lounge door handle, remove the spindle and refit the handle thus trapping the family in the room until my demands were met[:D]

I learnt a lot about negotiating at a very early age, it pays to negotiate from a dominant position, the first response is usually anger and threats which diminishes when the other party realises that you are standing firm and that they are in the weaker position.

[Gluestick]

You would have been of great use in the negotiations leading up the suspension of hostilities in Northern Ireland, JR.

Once Paisley had been locked in the room with McGuiness and Adams for a couple of days, his stomach would have compelled early accord!

My parents foolishly gave my elder brother a typical "Little Carpenter's Kit" one Christmas: he would have been about 5 or 6. In those far off days the tools were properly made replicas of adult's. He was discovered sitting underneath the 3/4 sized slate bed billiards-dining table, having almost unscrewed both legs at one end...................

One ought to have realised even then that he hadn't managed to work out the effect of cwts of slate bed falling on his embryo brain.

Perhaps five years later (he was then into electricity and crystal sets) he decided, one Christmas to examine the result of pushing two fretsaw blades into a 15 Amp socket (round pin no shutters in those days) and drop a further blade on top of the first two.

Finding a spare engineer from the Electricity Board on Christmas day to replace the main fuse proved impossible: so my father's younger brother, a fairly insane genius who worked for Marconi, cut the seals and inserted a bent nail for the duration, stating that "This is what we had to do in the Marconi factory during the war!"

Perhaps it's no surprise that elder brother finished up as a doctor of engineering and is even more insane now!

My thing originally was chemistry: and making interesting things that exploded; and small effective cannons. I took over the outhouse which I turned into a quite respectable lab and every birthday and christmas spare cash was invested in more and more equipment.

This all came to a sudden halt when one most interesting experiment with Nitrogen Tri-Iodide was enriched by me using concentrated nitric acid, made using a Leibig condenser constructed from a spare cocoa tin!

The resulting explosion was exciting to say the least...........................................................

Still, it was all much more fun than computer games.

[AnOther]

[quote user="J.Rs gone native"]I would have taken it apart as well, even if it had not played up[/quote]

And here's me thinking you'd learnt your lesson JR [Www][:)]

PS: Like Wooly the apostrophy in your name prevents quoting unless it is edited out [geek]

 

[Chancer]

Are you talking WW1 ammunition here Ernie?

I have learnt something from every painfull lesson in life but none of the results have stopped me from experimenting or being inquisitive, I somehow managed to have evaded Darwins principle so far.

If I havn't become sensible, grown up or been frightened off by now I guess that I never will.

Do I need to edit my username then? The pedant in me will find it hard to drop the apostrophy[:P]

[AnOther]

Bang on JR [;-)]

I was just being cheeky but I have to say I'm firmly with you in the intent to never grow up and give in to "normal".

It was the pedant in me that made me mention the ' but for informations sake only.

 

[Gyn_Paul]

Just to top and bottom this thread...

I put it all back together, taking the opportunity to move it from its position balanced on a couple of rafters at 1st floor level (it was transferred up there while we [poured the concrete, but all that wood amplifies the noise and I worry about the effect on the neighbours when the washing machine fills at 1h30) back down onto the concrete, and connected it up again and voila ! sa marche bien encore - actually better than before, I've cranked the trip pressure up to just over 3 bar, and beefed up the air to about 1.75 bar and the combination sems to give a good, even flow.

I'll gloss over the fact that I managed to keep the floor bone dry until I tried to find out why it seemed to be full but not pumping, and discovered I'd connected it the wrong way round and had to empty it again,

p

[sid]

I know you've got it fixed now, but I found this site useful for an explanation when I had the same problem with our well pump last year.

http://www.inspect-ny.com/water/watertank.htm

Sid

[Gyn_Paul]

Thanks for that, I had sort of worked out by trial-and-error that the big nut alters the whole on/off pressures, and the little one, the width of the range (what in electrical terms would probably be histerysis). But it's good to see it written down !

Suitably bookmarked for the future

p