New pool, trichlor tabs for the past 17 years, Where do I go from there?

[dmeyer]

I've bought a house with a 30K gallon pool, and I'm completely new to pool maintenance. It has a vinyl liner with an opaque cover, and since i'm in the northwest and rural we don't see a ton of warm sunny weather.

I bought a Taylor 2600 kit and tested yesterday, to this effect:

FC = 7.8
CC = 0
PH = 7.4
TA = 150
CH = 110

CYA was too high for me to measure, even after dilluting by half. I didn't try dilluting down beyond that level.

The CYA level is a bit alarming, but I guess it shouldn't be too surprising, given that the prior owner (I believe) was using trichlor pucks exclusively for chlorine the past 17 years. That said, he's been able to maintain this thing up to this point. In my residual inventory I have about 1/4 bucket of tabs left over, and another bucket still sealed (and thus, returnable), and a huge bag of baking soda. The water in the pool looks great and is pleasant to swim in.

I'm taking any and all advice at this point. My sense of this (which I post only so knowledgeable people here can straighten me out) is to take the sealed bucket of tablets back and go with calcium hypo or bleach for a while, to increase the FC level. I'm also inclined to use rainy days (and we get lots of them) to dillute and then drain the pool a bit trying to get the CYA under control, but maybe that's more trouble than its worth in that it would require a corresponding chlorine boost. Is there a point to continuing to try to further dillute CYA samples until i get an estimated level? Without that I would seem to lack a hard target for TA and FC.

My goal is to get through the year with some light use of the pool and minimal hassles, while learning to manage this thing myself.

[Watermom]

Definitely no more trichlor and also no dichlor powder which is also stabilized which means it has CYA in it.

Go ahead and try (within reason) and dilute a little further to see if you can get a basic idea of the CYA level. Report back if you get any kind of ballpark number.

If it were my pool and had sky-high CYA, I would probably do a series of partial drains over time and try and get the CYA level down to a more manageable level. But, let's see what you find out. It may be better to just try and coast through this year and drain a considerable amount over the winter and dilute as you refill in the spring next year. If it is REALLY high, even doing that may not reduce it to a 'normal' level and the process will take a few years to do.

One big concern ---- Sometimes over the winter, CYA biodegrades and ammonia is produced as a byproduct. It is EXTREMELY hard to get rid of all the ammonia. If you only have a little CYA in a pool that biodegrades, it is hard enough. But, a pool with a LOT of CYA is even harder. This doesn't happen to all pools and there is no way to tell which pools it will happen to.

Let's not worry about that for the moment. Just see if you can get a ballpark 'guesstimate' of your level. Then, we'll advise you from there.

MORAL OF THE STORY for other pool owners who may be reading: You CANNOT use trichlor tabs or dichlor shock for an indefinite period of time in a pool without consequences!

[dmeyer]

UPDATE: I dilluted a sample down to 1/4th and arrived at just under 240ppm CYA.

For what it's worth, I also found some old water analysis done by a national chain. They found that CYA was 121 this time last year, and in 2010 it was 161.

Finally, I no longer believe the 30k gallon number (which is from that same shop) is accurate. I think the real number is in the 20-25K gallon range, probably closer to 20K gallons.

[PoolDoc]

Order a K2006 (Amazon link in my signature) if you don't have one (not sure what a "Taylor 2600", above, is), then read the Best Guess page, linked in my signature.

Using the CYA test from the Taylor 2006, do a careful test on a mix of 3/4 cup tap water + 1/4 cup pool water for CYA to establish your actual CYA level (= 4x test result level!)

Begin operating with chlorine levels from the Best Guess chart -- for CYA = 150, probably you want to dose to near 20 ppm FC, and let the pool 'coast' till it reaches 10 ppm. Brush on days when chlorine is high.

Read the polyquat page, and stockpile 2 quarts of polyquat per 10K gallons of pool water. It's currently about $17 @ Amazon, with free shipping and no tax in many states. Begin using polyquat at first sign of algae, rather than 'shocking' to levels of 30+ ppm.

Otherwise, swim and enjoy. 20 ppm FC is *not* a problem when CYA = 150 ppm, though you might not want to wear brand new expensive fashion swim suits in it. Skin is far, far more chlorine resistant than fashion Lycra.

Ironically, operating this way may be both EASIER and CHEAPER than doing a more normal operation. You'll probably be able to dose with bleach or cal hypo just 1x per week!

If you use cal hypo, keep an eye on your calcium levels and pH.

When testing pH, take your readings within 10 seconds of adding phenol red. When FC > 10 ppm, use ONLY the Taylor reagents. The high chlorine will invalidate your pH readings, if you let the sample sit before reading.

Good luck!

[dmeyer]

Order a K2006 (Amazon link in my signature) if you don't have one (not sure what a "Taylor 2600", above, is), then read the Best Guess page, linked in my signature.

Using the CYA test from the Taylor 2006, do a careful test on a mix of 3/4 cup tap water + 1/4 cup pool water for CYA to establish your actual CYA level (= 4x test result level!)

I'm using the K2006, and I used the method you describe above to estimate a CYA level of 240.

Begin operating with chlorine levels from the Best Guess chart -- for CYA = 150, probably you want to dose to near 20 ppm FC, and let the pool 'coast' till it reaches 10 ppm. Brush on days when chlorine is high.

At a CYA over 200, It seems I'm off the chart, but I suppose I should still be cruising around 10-20ppm of chlorine? The chart is a bit wide open at the high end.

Read the polyquat page, and stockpile 2 quarts of polyquat per 10K gallons of pool water. It's currently about $17 @ Amazon, with free shipping and no tax in many states. Begin using polyquat at first sign of chlorine, rather than 'shocking' to levels of 30+ ppm.

Will do! I think you mean for me to use polyquat at the first sign of algea?

Otherwise, swim and enjoy. 20 ppm FC is *not* a problem when CYA = 150 ppm, though you might not want to wear brand new expensive fashion swim suits in it. Skin is far, far more chlorine resistant than fashion Lycra.

Ironically, operating this way may be both EASIER and CHEAPER than doing a more normal operation. You'll probably be able to dose with bleach or cal hypo just 1x per week!

If you use cal hypo, keep an eye on your calcium levels and pH.

When testing pH, take your readings within 10 seconds of adding phenol red. When FC > 10 ppm, use ONLY the Taylor reagents. The high chlorine will invalidate your pH readings, if you let the sample sit before reading.

Good luck!

Gotcha. Sounds like a plan.

[Watermom]

He did mean "at the first sign of algae." I had already caught that and fixed it in his post above.