Frustrating Experience W/ A Friend's Pool

[jkusmier]

Background: a buddy of mine was having problems maintaining FC in his pool. He was using test strips so I paid a visit w/ my Taylor K-2006 a couple of weeks ago. Sure enough, FC read 0 (even though he'd added 6 lbs of calhypo that morning). I didn't bother to test CC as I suspected his CYA was sky high (he's been using trichlor pucks and calhypo). Sure enough, CYA was over 100. I advised him to do a partial drain/refill and start using chlorinating liquid or get a SWG. He drained 18-24" from his ~29,000 Gal vinyl-lined pool, refilled and shocked w/ approx shocked w/ 10% chlorinating liquid. I did not re-test at that time.

He left for vacation last Tue but made arrangements to have a SWG installed by a very reputable local pool company (Dugger - curious as to whether anyone here has heard of them?) last Thu. I spoke w/ the tech before he went out for the install, advised him of the CYA and told him to set the SWG to 100% initially. Spoke w/ another family member that night, told him to brush the salt and reduce the SWG's output to 60% the next (Fri) night. Finally stopped by tonight to check the pool. All levels appeared fairly good: FC was a bit low (2.0), pH was 8.0, TA was 90, CH was 150 and CYA was 55-60 (decent for what was now a salt pool). I was about to add some chlorinating liquid, some dry acid and head home when I realized that the water level was low - about 3/4" above the bottom of the skimmer weir. Now comes the fun and the questions.

I immediately threw a hose into the pool and went to empty/rinse the pump basket. When I restarted the pump I had a devil of a time getting the pump primed. Messed w/ the valves (he only has two), thinking one controlled the mains and the other controlled the skimmers. After about 20 mins I realized that one valve controls one skimmer and the other controls the other skimmer. I assume each is also tied to one of the mains but, to be honest, I don't even know whether the main are working or not. Seemed like an odd plumbing job (I'm pretty sure the prior homeowner who had the pool installed did alot of the work himself) for a couple of reasons: 1) even if you close one skimmer, you're still apparently using a main w/ the other skimmer - when vacumming, I prefer to close my mains for maximum suction when vacuuming and 2) if your pool water level is low, you can't simply close the skimmers and circulate w/ the mains while re-filling, but must instead kill the pump - which is what I did.

Threw a second hose into the pool and got the water level up about 1" within an hour, closed the valve to the far skimmer and placed the hose in the pump to prime. Let it run a good 5 mins and while the water level in the pot raised it never topped out/overflowed. Finally gave up and started the pump - it wasn't dry but the pressure gauge never moved and I felt no flow from the returns. Eventually I tried backwashing the filter (an undersized Pentair Sand Dollar) and there was good flow from the backwash line - of really, really brown water (my friend isn't high on pool maintenance). So the pump was definitely working. Stopped after a couple of minutes (a thorough backwash cycle wasn't my main objective at this point, I wanted to go home), rinsed for 30 seconds, then set to filter (stopping and re-starting the pump each time before cycling the multiport). Again, no flow from the returns but the pressure gauge jumped from 20 to 30 psi. Cycled back and forth from backwash, rinse, waste and filter a few times - again, plenty of flow from the backwash line during backwash, rinse and waste but never could get flow from the returns when the multiport was set to filter.

I finally gave up, killed the pump, told a family member to let the pool re-fill to the middle of the skimmer faceplates or higher and went home.

WTF is going on? I was thinking the skimmers had been sucking air for a day or two and damaged the pump, but as I noted above 1) each skimmer appears joined to a main drain and 2) the pump was having no problem in the backwash, rinse and waste settings.

NOTE: before I stopped the pump the first time to rinse the pump basket I noticed the pot was full to the lid-top. Never could get it to fill again.

Stopped by for what I thought was a 10-minute chore, ended up spending 2 hours and leaving very frustrated and perplexed.

Thanks for any insight.

[jkusmier]

Another note: my friend's pool had ALOT of wrinkles on the bottom. They weren't there before he did the partial drain/refill (and he didn't drain that much water). I didn't think this was possible in a liner as old as his (house was built in 1999, I think pool was probably installed in 2001-2002). He's planning to have a new liner installed this fall or next spring. Also, large, strange blue/green stains have appeared in a few spots in the shallow section. Brushing doesn't help - what would cause that? Doesn't seem like a metal stain... He hasn't used a copper-based algaecide to my knowledge and doesn't have a heater...

[quantumchromodynamics]

Sure enough, FC read 0 (even though he'd added 6 lbs of calhypo that morning). I didn't bother to test CC as I suspected his CYA was sky high (he's been using trichlor pucks and calhypo). Sure enough, CYA was over 100.

You should have tested for CC. The high cyanuric acid level would not have affected that. After adding 6 pounds of cal hypo, there should have been a strong chlorine reading (FC or CC for a total of about 15 ppm) unless the cyanuric acid was low and the chlorine had time to be depleted by the sun or there was some sort of large organic demand (was there visible algae?).

Again, no flow from the returns but the pressure gauge jumped from 20 to 30 psi.

Most likely a blockage in the return line. I suspect debris clogging the new salt cell. Remove the cell and clean as needed.

Another note: my friend's pool had ALOT of wrinkles on the bottom. They weren't there before he did the partial drain/refill (and he didn't drain that much water)

Most likely due to high ground water levels, especially if he drained the pool water out onto the ground near the pool. Is there some sort of water nearby that can give an indication of ground water levels? Like a nearby pond etc?

Also, large, strange blue/green stains have appeared in a few spots in the shallow section.

Most likely copper. Lower the pH to see if that helps. Also, try ascorbic acid on a small test spot to see what happens.

[AFiremanFirst]

I agree! Cells typically don't cause much of an increase in pressure but a blockage before the cell could. Take the cell off. Turn the system on. Does water blow out! I bet it does. How was the jet pressure prior to addition to swg? Sounds like you're covering all your bases. Note a pump that runs dry will typically trip its thermal relay which will reset when it cools. Uncommon to cause damage. Your pot basket will not fill full with out the lid on because the water drains back down to the pool. Unless you close the 2 valves you spoke of. But that really isn't necessary.

[jkusmier]

Thanks for the suggestions - the problem turned out to be embarrassingly simple. My friend's father-in-law was present, and when I told him to turn the leftmost valve while I was observing the far skimmer he turned the anti-siphon valve on the return line after the SWG. It never occurred to me to check to see whether the valve was open or closed. Hence no problem moving water out of the backflow hose! I re-started the pump and all is fine. quantum, you were right, I should have checked CC - there was plenty of it. My friend returns tonight and I'll tell him to dump a case of 10% chlorinating liquid in the pool tomorrow night and re-start the SWG the next AM.

[quantumchromodynamics]

The rapid loss of FC and the high CC is a concern. It's important to maintain shock level until the problem is resolved.

It's possible that bacteria are converting cyanuric acid into ammonia. You should get an ammonia test kit to test for ammonia levels. You should also monitor cyanuric acid levels to see if there is any drop, although the test is usually not accurate enough to measure small movements.

[jkusmier]

The rapid loss of FC and the high CC is a concern. It's important to maintain shock level until the problem is resolved.

It's possible that bacteria are converting cyanuric acid into ammonia. You should get an ammonia test kit to test for ammonia levels. You should also monitor cyanuric acid levels to see if there is any drop, although the test is usually not accurate enough to measure small movements.

I believe it was simply a result of the high CYA. He had no idea that it was so high and never used enough shock to achieve breakthrough, so he ended up w/ increasing CC. I garbled my first post - after partially draining/refilling he shocked w/ 6 jugs of Vertex (10%), and I told the tech who installed the SWG 2 days later to set output to 100%. My friend added another 4 jugs of Vertex this morning. That apparently did the trick - this afternoon, FC was at 4.0, CC was 0 and CYA was 50. His next problems are an undersized sand filter and no control board to precisely control the SWG's output and pump run times. He has alot to learn! Hopefully he'll be able to find the sweet spot for output and run-time and adhere to it. Thanks for a very informative response - the reason why I keep coming back here!

[quantumchromodynamics]

The question is, where did the ammonia, or other contaminants, come from that caused the CC? Unless there is some explanation for the source, such as many kids urinating in the water, I think that it is possible that it could have been due to bacteria.

Your first post notes a cyanuric acid level of over 100. Now the result is 50 ppm. Assuming no test error, it seems like some loss of cyanuric acid. [Edit] I forgot about the partial drain and refill, which would explain some of the cyanuric acid loss.[End edit]

Either way, it now seems that the problem has been resolved.

If possible, try to get him to get a good test kit.

[jkusmier]

I think the CC was a result of poor management from opening this spring. Pool parties, sunblock, body oil, etc. - the usual suspects. And guesswork re: shocking.