Water change?

Aug 15, 2013
3
I've learned on this site that TDS level has no bearing on when to change pool water. Are high CH and/or high CYA levels the only conditions which would require draining a pool or having an RO treatment?
 
Welcome to TFP!

Yup. Those are about the only 2 I can think of. Unless you have a swamp and a tiny pool or maybe a Baq conversion, but those could be solved with chlorine.
 
Does performing RO on a high bather load pool make it easier to care for, or is it a waste of money? I've been seeing some articles on RO lately and before finding this site, thought it sounded like something this side of miraculous. As you can see I'm having trouble letting go of years of conditioning that pool water had to be changed every 3-5 years.
 
Bather load should have nothing to do with need to replace water or perform RO treatment. While there is much talk about RO treatment, the simple truth is the service is available in very few places (mostly select parts of southern California and Arizona) these are primarily areas with very high CH fill water, so water replacement only goes part way in solving the problem, and CH starts building again due to evaporative concentration. Even in these areas the economics of RO treatments are questionable, as the cost of the service often exceeds the cost of substantial water replacement. Cost of RO treatment may come down in the future as there have been multiple advances in the technology in the last couple of years that has the potential of greatly lowering operating pressures needed for RO membranes (from the 1,200+ psi ballpark, down to the 150-300 psi range).

To sum it up water replacement should only ever be considered for:

High CYA, High CH, high metal content if a low metal content fill water is an option (high metals caused by long term use of of copper containing algaecide, or trucked in water being used as an alternative to well containing high metal levels), or possibly some exotic type of contamination
 
Thanks for the replies to all of you, and thanks for the welcome. I'm not having a problem, as I said in my earlier post, I've been reading a lot about Reverse Osmosis as an alternative to pool draining. I understand that it's more expensive than drain and refill, but from an environmental standpoint, it's much more responsible than dumping thousands of gallons of H2O. I was thinking that RO for pools might be a growth business here in Southern California as water conservation is important. However, as I'm learning on this site, the number one selling point for water change, high TDS, is a somewhat meaningless measurement. So now I'm wondering if an RO business makes sense, if there are so few reasons to change pool water.
 
RO makes sense if CH, CYA, metals, or salt is high. Salt would only be high if somebody has a salt water chlorine generator (SWG) and accidentally put too much in, it is very rarely a problem for pools without one. CH can cause unsightly scaling if it is too high and the pH rises too high, but is usually a problem that can be controlled without much extra work. CYA is introduced either by itself as stabilizer or through the use of pucks which are made of trichlor, or powder made of trichlor or dichlor. CYA can be a big problem if it rises too high and is the main reason to consider RO.

So are you thinking of getting your pool treated, or considering looking in to starting/investing in an RO business?
 
Wow, who came up with using environmental concerns to market RO pool treatment vs water replacement, that is about the best one I have heard since the health benefits of smoking. On an industrial scale about the best RO can do in terms of energy consumed is around 3 KWH per cubic meter with the current technology, power consumption on a smaller scale is even worse. Most on site RO treatments I have seen use diesel engine powered RO treatment trailers since larger enough electrical supplies to run large RO pumps are typically not available around swimming pools. ( to give you an idea of the electrical supply size needed I know of at least one 2 GPM RO desalination unit that uses a 1.5 HP motor to drive it, which is about the same size motor as is used on a typical pool pump, 2 GPM = 120 GPH, or only 1880 GPD). Also keep in mind that a typical RO set up looses 15-20% of water as waste that must go down the drain to flush out the removed material from the RO membranes.

Ike
 
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