[/quote]
"Why two stages?"

If you drain too much water from a solid pool (gunite, plaster, fiberglass) and the ground water level is high, the pool can float up in its hole -- tearing up the pipes and in general, ruining the pool owners day.

Draining too much water from vinyl lined pool can result in the liner floating off the bottom of the pool. Not as bad as the previous example, but still one of those things that just doesn't need to happen.

Another benefit of using R/O! Since the water that is lost in the brine solution is returned with make up water, the plaster is never exposed nor does the water elevation ever drop much lower, if any, from its initial elevation. No opportunity for plaster damage or floating pools!

Am I incorrect in remembering that the CYA test in the TF100 is limited to detecting 100 ppm, and above that will still read as only 100ppm? If I am right, your original CYA level could be higher, maybe by a significant amount. Diluting the sample may help, but you still lose accuracy doing this.

Yes, that is correct. The same is true for most of the common CYA tests. Some test strips will read higher levels, up to 300 in some cases, but they often suffer from accuracy problems.

You can use dilution, mix one part of pool water with one part of tap water, test that, and then multiply the result of the test by two, to measure higher levels approximately. However, dilution significantly reduces the precision of the test (which is fairly low to begin with).

Ok so the verdict is in:

Reverse Osmosis works brilliantly!

Got the guys from Pool Services Technologies in and they rigged up their truck which contained the filter and reverse osmosis membranes. They even have their own generator so they're not using your electricity!

So original numbers were:

FC 7
CC 0.5
pH 8
TA 100
CH >800
CYA >100
TDS 4660

10 hrs of filtering and here are the numbers tested with my kit:

FC 10.5 (FC was 0 once they'd finished so they added bleach to give FC 10.5)
CC 0.5
pH 7.2 (they brought it down from pH 8 with muriatic acid to try and dissolve some of the calcium build up on tiles at water line)
TA 40
CH 130
CYA <20 (no really!! tested it twice....no cloudiness at all..brilliant)
TDS 615

There numbers are in agreement with Bruce and Sal's numbers after they'd finished the RO job so that's TWO independent testings.

Will get some stabilizer tomorrow to bring it up to 30 and will probably throw in some baking soda after it's been at pH 7.2 for a few days, to bring the TA up.

Couldn't be happier with the result and would highly recommend their services. And considering we're in San Diego with a drought and water restrictions, we also have that warm fuzzy feeling because we didn't waste 10,000 gallons of water.

Cheers,
Fiona

Glad to hear the R/O worked. Since you probably still have the pucks and float I thought I would point out that you can use them to add that extra ten PPM of CYA and skip a trip to the pool store.

That is a great update! Thanks for sharing.

I second the motion. In your pool, each 8-oz tab would be worth about 2ppm CYA. I have tabs in my pool now, to replace CYA lost over the winter.
--paulr

Fiona,

Thanks for the opportunity!

Glad to hear it worked so well! Seems like great technology, wish it were available in my neck of the woods!

Thank you for the kind words, Fiona! You were a pleasure to work with!

I have basically the same situation. CYA over 100, CH 700+ (stopped at 70 drops) high TDS. I live in Ventura. Pool ~28k gal. I'd like to get an estimate on the RO.

Thanks,
Steve

hmm...never even thought of using RO for the pool. I have a 125 gallon saltwater fish tank with hard and soft corals and needless to say water chemisty and lighting are very important..I have an RO/DI setup to replenish tank water..but it only produces about 30 gallons of RO water per day.......How does the pool setup work to be able to filter water so quickly????

We can filter 40,000+ gallons a day, so we are a little larger than your aquarium unit You get the idea though, since you are utilizing the technology on your aquarium

Feel free to PM me if you would like more info or a referral in your area. Thanks!