New Pool Owner - Chlorine not holding

[denastar]

Hello - We bought a home that had a closed inground pool for 2 years. The pool is open now and is clear and clean. However, it seems like it will not hold Chlorine? We have a chlorinator - which have been told by servicing people it will not hold a level until there is a consistnt level to hold. We have shocked it numerous times, and haven't shut the pump off at all. I thought it was supposed to always run? Anyway - the chlorinator has had tablets in it for 3 weeks, when they first opened the pool the they connected it for previous owner bypassed it, a week later we noticed this and put it on high, have shocked it with 2 cases, then a case and a half since, and the readings on chlorine are still virtually zero. The pool itself is open and ready - but what do I do about chlorine?

[Watermom]

I would turn off the chlorinator for now. My guess is that the pool had CYA in it at one time which has biodegraded into ammonia. We see this a lot when people are opening pools in the spring. In fact, we have several threads going right now where people are in the middle of this problem. The only way to correct it is with lots of chlorine. At some point, the chlorine will hold but it can take awhile. You can't shock a pool with trichlor tabs. For now, just use plain, unscented household bleach --- generic is fine.

You will need to give us more information about your pool. Type, volume, type of filter, size of pump and exactly what all you have put into the water --- meaning ingredients. It is also going to be necessary to have a good test kit. The one we recommend is the Taylor K-2006 or 2006C which you can get through the link in my signature. Try and order one asap so you'll get it quickly.

We need some current water testing results. Until you can get a good kit, at the minimum, go to Walmart and get an OTO/Phenol Red kit (yellow and red drops). If they have the HTH 6-way kit, that one would also suffice until you get a good one.

Come back with more info and somebody here will try and help.

Lose the servicing people. Any one who is supposedly in the pool business that tells you that, "it will not hold a chlorine level until there is a consistent level to hold" doesn't have a clue about taking care of a pool.

Welcome to the Pool Forum!

[PoolDoc]

Just to explain a little further: contrary to what the pool industry generally believes, cyanuric acid can be bio-degraded (eaten!) by bacteria. The bacteria can then 'poop' one of three things: nitrogen gas, which causes no problems; nitrates, which causes no immediate problem, but fertilizes algae later; and ammonia, which is a huge problem, so much that you could think of it as 'negative chlorine'.

Depending on how the bacteria have gone about things, it make take nearly 1.5 ppm of chlorine to clean up the residue from each ppm of CYA that's missing from your pool. That may not sound too bad, but what it means is that if you had 70 ppm of CYA last fall (pretty common) and none now, you may have to add 100 ppm of chlorine to your pool, before you are able to maintain a residual.

Until you have done so, you will either have to (a) drain and refill your pool or (b) add dose after dose of chlorine, till the ammonia is gone.

Just a reminder: draining your pool can be very dangerous to your pool. Vinyl liners are often destroyed when inground pools are drained; if the ground is wet, concrete and especially fiberglass pools can literally float out of the ground, when drained , and so forth. You'd better be sure it's safe before your start.

Most people are left with the need to clean up their pool water as it sits.

[AnnaK]

I have a pool that ends a season with around 50 ppm CYA and starts the next season with 0 ppm. Ben, how does a pool owner know which of the three situations you described above the pool comes under: nitrogen gas, nitrates, or ammonia? If the CYA was converted to ammonia, would there be a smell?

I start each season by adding enough CYA to get to 20 ppm (calculated, since I can't measure that low), add liquid chlorine to 10 ppm, and then run the trichlor chlorinator for a while, usually until it gets hot toward the end of May. Then I switch to just LC. My starting water has always been clear despite a fair amount of organic debris that blew in over winter.

Given my personal experience, is it valid to say the CYA in my pool is NOT converted to ammonia? Or to nitrates, because I don't have a problem maintaining chlorine? That would then be the 'test' , wouldn't it, whether the pool holds chlorine at startup?

[PoolDoc]

I have a pool that ends a season with around 50 ppm CYA and starts the next season with 0 ppm. Ben, how does a pool owner know which of the three situations you described above the pool comes under: nitrogen gas, nitrates, or ammonia? If the CYA was converted to ammonia, would there be a smell?

It's possible to test for both nitrates and ammonia, but we haven't checked to see which kits are reliable. We probably need to look for some ammonia kits, maybe from the aquarium side of things.

As far as I know, a kit is the ONLY way to tell if CYA has gone to nitrates. During startup, a pool that has lost CYA over the winter should be behave pretty much the same, regardless of whether the CYA went to nitrogen gas, or nitrates.

However, the tell-tale for ammonia will be rapid conversion of added FC to CC, followed by lost of chlorine: like this:

PM: Add 10ppm FC
Later, PM: FC-5 ppm, CC-3 ppm
AM: FC 1 ppm; CC 2 ppm
(not actual results, but typical of what we're seeing)

One very IMPORTANT fact to remind people of: when they add chlorine, they are NOT wasting it. Rather, they are getting rid of the ammonia. Also, without actual ammonia testing, the only way to tell when you're done (or getting close) is that the FC:CC ratio will get larger and larger, and the loss overnight will diminish, so you might see this:

PM: Add 10ppm FC
Later, PM: FC-6 ppm, CC-1 ppm
AM: FC 4 ppm; CC 1.5 ppm
(not actual results)

[AnnaK]

Thanks a lot for the clarification.