Reverse osmosis for pool?

Just back from a few days in Miami and what fun! They have supermarkets for everything - even pools!

Like a child looking in the window of a candy store, I could not resist trying them out. One in particular with a lovely name: Pinch a Penny. What I had not bargained for though was the US art of securing a sale. Unlike here where one can walk in where the vendeurs just look at you, in the US of course one is suddenly the sales assistants best friend!

I had to think up something quick to escape the chap’s clutches. So I blurted out that my problem was that no one made one instrument to test for everything. But no, he marched down a couple of aisles and pulled off a blister pack with a ‘Pool eXact EZ’ tester and proudly boasted he had everything! Yep, this thing tests Cl, Ph, TA, CY - same as my little blue thing, but also tests for hardness, salt and phosphates using DPD. So I was obliged to buy it after all that . 140 bucks! Then sir, as you are in Europe, you will need a supply of DPD. Another 140 bucks for two years worth… He was a happy bunny and gave me a lolipop on the way out. I tried the tester this morning - it works!

Anyway, I digress. He was telling me how water restrictions are hitting various neighbourhoods and that he at Pinch a Penny is seriously promoting reverse osmosis for pools. Initially the use a trailer service for those who drain their pools each winter with quite some success, but recently have been installing little hang-on-the-wall systems that continuously recycle the pool water. Of course he was trying to sell my one, but even he appreciated that there is a limit to what you can take onto and aircraft… I see these things also advertised a little in France - are they any good? Would they help in any way on saving water that ordinarily might be sent to waste>

sounds like a question for @Corona

Why on earth would one do that? Surely the whole idea is to keep the water in the pool so that the pool remains stable/in the ground.

We have had to drain rain water from our pool at least six times this winter because the pool is constantly filling up so that the water level is above the skimmer. Never known a winter like it.

Yes, question aimed for Corona and other water experts.

Not all empty pools pop out of the ground - only where there is a high water table.

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Oh golly gee it must be better its American :joy:

Reverse osmosis, a friend in America used to run a truck mounted RO service as some of the water is not fit for swimming in. RO strips most things from water you end up putting them back in afterwards. Around 25-30% of the water is wasted in RO treatment as the filters need backwashing to remove the dirt and salts and calcium etc. Interestingly in large commercial units AFM is often used to pre filter the feed water for RO filtration as it removes so much from the water and saves wasting so much backwashing the RO membranes/ceramic filtration.
I know the EXact micro series of testers and used to grab a coffee with the CEO when we met up every couple of years. Haven’t seen her in a while but maybe I will in November.
There isn’t much to be gained from RO in our usage and the extra power it would take compared to using AFM correctly with a bit of flocculent. Dodgy polluted US water on the other hand might help remove the toxic heavy metals etc they have in some water supplies. When you consider how US pools have filtration that is too small for the pools but also pumps 2x the size they need to be its no wonder they are always looking for another system to sort out the issues.

Better in the US? Certainly better served! At least the chaps I spoke to were able to converse pools - maybe not at your level - but better than the ones in Cash Piscines here…

I was not clear in my interest in reverse osmosis. It is not to replace the SWG and filter, but to use to recycle waste water, or most of it.

I moved my pump and installed my in-line air venturi, replaced the Zodiac SWG plates and filled the filter with AFM. I now have a sparkling pool! It was pretty sparkly before, but now maybe more so - or maybe it is psychological… The venturi is a great success giving me a steady stream of fine bubbles without any poolside ‘hiss’:

I now have all the pipework in place to collect some roof water and pool overflow, just waiting for the 3M3 tank. With about 150 M2 at 450mm rainfall, I should fill up very quickly and hope that for next year I shall be truly eco in pool top ups…

Whilst in eco mode, I thought of making a sediment tank from a cube into which I could send all the waste water from backwashes. It is here where I wonder if a small RO plant might be beneficial. Instead of a sediment tank, the waste water would be collected in a cube and whilst discharging the waste, the RO plant would kick in and send fresh water back to its origin. Yes, the waste water from the RO would be lost, but not as much as before. maybe an expensive way to do it, but hey, it would certainly show the authorities that I am responsible, which, at the end of the day what it is all about.

Aha, understand now collection and treatment of waste/rainwater. As explained prior, ultrafiltration like RO is not without issue as the tiny pores in the filters will rapidly clog hence best to pre filter. Water treatment companies or some like Welsh water and Scotish water use AFM in the past it was sand but as we know AFM is far better. You would need to frequently backwash the RO filters with very clean water, you see where this is heading? In your situation I would harvest the water and run that through a separate AFM filter thats far easier and cheaper energy wise to opperate. That will remove eveything down to 1 micron which is more than sufficient for your usage. I owe you a sketch, will sort that this week hopefully, v busy working on the house and not learning sketchup.


I hear you! Yes, maybe too fiddly for a small task. It gets stupid when one has to backwash the backwash!

Back to my basic idea of wasting into a sediment tank. Maybe a piece of string question, but how long might it take for the sediment of >2 microns to settle of say, a 500 litre avearge backwash? A week maybe?

Good question, the finer the particles the longer they stay in suspension and you need very still water. Thats why water companies use flocculent to speed up the process. You may consider, depending on your setup to use something like the Waterco multi cyclone ( Dyson for water) removes quite a lot of dirt and minimal wastage of water.