How often to change small pool water

[nephilim]

We have a small pool for the kids just for them to cool off a bit, it is only 8ft round by about 2ft deep. How often should the water be changed so it stays safe for them. Can chemicals be added to a small pool like this or is it just a case of changing the water. Thanks.

[Poolguy]

A small pool is the same thing as a big pool and the same laws and principles apply.

You should test the water and add the sanatiser that is required, very small doses only I would suspect.

You will also need to filter it to ensure that it remains clean.

If you can't be bothered with all that then empty it after every use and refill for the next use. Logic.

Andrew

[AnOther]

Refilling could be easier and cheaper than the cost of chemicals but emptying water at say 24/25/26 deg etc. to replace with considerably colder water from the mains might not go down too well with the little darlings [blink]

[nephilim]

Thanks for that, so would replacing the water say every 2-3 days be ok, it takes about half a day to fill. Poolguy, you mentioned 'Laws', what do I need to be aware of with a pool like this, it is obviously above ground.

[AnOther]

I think by 'laws' Poolguy is referring to those of chemistry not as in legal [;-)]

[chem geek]

The guideline used in the U.S. for the Water Replacement Interval (WRI) for commercial/public spas is:

WRI (days) = (1/3) x (Spa Volume in U.S. Gallons) / (Number of Bathers per Day)

The presumed soak time is around 20 minutes and the temperature is hot (100-104F).  The above translates into changing 3 gallons of water for every bather use.  In a pool, the amount of sweat/urine relative to a spa is probably around half, but people stay in the pool longer.  In commercial/public pools, the water replacement is at 7 gallons for every bather but this is continual replacement and roughly translates to 1.5 gallons of absolute replacement (i.e. if 7 gallons represented 99% effective water replacement, then this is equivalent to an absolute 1.5 gallon replacement without continuous dilution).  DIN 19643-1 says 30 liters of (continuous) water replacement which is roughly 8 gallons.

Your 8 foot round 2 foot deep "pool" is around 100 cubic feet or 750 gallons.  The WRI from the above formula for 2 bathers would be 125 days or around 4 months.  However, kids tend to urinate more in pools and they may stay in the pool for a longer time.  Nevertheless, there should be no need to change the water every few days.  I would think you could go for at least a month and be OK.  As PoolGuy (Andrew) mentioned, just treat the water as you would any pool.  Have some Cyanuric Acid (CYA) in the water to protect the chlorine from sunlight and to moderate the chorine's strength and then just maintain sufficient Free Chlorine (FC) in the pool so that it is sanitary.  pH and TA should be maintained as well.

Richard

[AnOther]

Well that told you nephelim [:)]

I bow to your knowledge and expertise chem geek and wouldn't presume to disagree or argue however I can't help wondering just how many of the millions of pools in use in France, and indeed the world, benefit from a fraction of what you describe [blink]