Pool opening questions: chemistry, cleaning, pool deck care

[bc1080]

Hi all, just wanted to ask a few questions while gearing up for the coming season. This is our 3rd year with this pool (came with current house). I’m still new to this and don’t know what I don’t know, so some of these questions may be kind of obvious.

1. Testing when opening last summer showed almost no salt or CYA in the water (had stable chemistry at the end of last season), which didn’t make sense as I thought those chemicals should stay around and only dilution from discharge to waste/refilling would really change those values. I had to add over 300 lbs of salt. Are there any possible reasons for this or is that within a normal range?
2. I've had a hard time maintaining pH, it seems to want to settle around 7.8 by itself but sometimes goes higher. I’ve seen various comments on what is acceptable. I was wondering if that was OK for a salt pool with a nearly always running pump, it didn’t seem to cause any issues with swimming.
3. Are you supposed to seal cracks in the surrounding pool deck? We got a new liner in 2023 and quickly several mini canyons started forming underneath. I know liners with sand bottoms are never real smooth, but these are so bad that people have tripped and it is almost impossible to get a vacuum or brush into many of them. The only thing I can figure is that ground water/runoff is getting under the liner and channeling out the sand. This pool's 30+ years old so there are many cracks in the concrete deck, many are unsealed, maybe water is getting in those cracks and running under the pool?
4. I have also learned that our sand filter may also be undersized, the installed S200 doesn’t seem like the recommended unit for ~28k gallons. Plus, our pool seems to consistently have a pretty high filtration demand due to all the dust and tree junk that falls in there. I am going to change the sand (suspect the prev. owner didn’t use proper pool sand & I have to replace the O-ring anyway), and didn’t know if I should use something other than the normal filter sand that might do a better job considering the demand. The reason I ask is that I have seen some sand alternatives say you can use less by weight, but not sure that means I'd be able to add more (not sure if it would cause flow issues, etc.)

Thanks!

 

[PoolStored]

1. Testing when opening last summer showed almost no salt or CYA in the water (had stable chemistry at the end of last season), which didn’t make sense as I thought those chemicals should stay around and only dilution from discharge to waste/refilling would really change those values. I had to add over 300 lbs of salt. Are there any possible reasons for this or is that within a normal range?

CYA will degrade. Salt will be replaced if you had a lot of water and removed water. Before adjusting any chemicals you should run the pool for 24 hours before testing and adjusting. Did you do that? The rain during the winter stratifies and stays on the top. So if you didn't pump, and took sample from the test, that is why it is zero.

I've had a hard time maintaining pH, it seems to want to settle around 7.8 by itself but sometimes goes higher. I’ve seen various comments on what is acceptable. I was wondering if that was OK for a salt pool with a nearly always running pump, it didn’t seem to cause any issues with swimming.

Absolutely fine. Any pH 7.0 to (and including) 8.0 is fine.

Are you supposed to seal cracks in the surrounding pool deck? We got a new liner in 2023 and quickly several mini canyons started forming underneath. I know liners with sand bottoms are never real smooth, but these are so bad that people have tripped and it is almost impossible to get a vacuum or brush into many of them. The only thing I can figure is that ground water/runoff is getting under the liner and channeling out the sand. This pool's 30+ years old so there are many cracks in the concrete deck, many are unsealed, maybe water is getting in those cracks and running under the pool?

Post pictures so we can see what we are dealing with...

I have also learned that our sand filter may also be undersized, the installed S200 doesn’t seem like the recommended unit for ~28k gallons. Plus, our pool seems to consistently have a pretty high filtration demand due to all the dust and tree junk that falls in there. I am going to change the sand (suspect the prev. owner didn’t use proper pool sand & I have to replace the O-ring anyway), and didn’t know if I should use something other than the normal filter sand that might do a better job considering the demand. The reason I ask is that I have seen some sand alternatives say you can use less by weight, but not sure that means I'd be able to add more (not sure if it would cause flow issues, etc.)

S200 is a fine filter. In general we recommend getting the largest filter you can afford. Do not use sand alternatives. Sand is the best for a sand filter.

 

[bc1080]

Thanks for the response!
To answer, I had let the pool run for a few days before that testing (I was wondering why I not able to build chlorine levels with the generator).
Good to hear the S200 should work nicely, that eliminates one thing to wonder about. I'm thinking that other "capacity" figure was geared to upsell more expensive filters, based on the turnover rating it does seem like it should be fine. Will continue with my planned sand refill, already had some on order at ACE.
Also reassuring on the pH. The amount of dry acid I put in last year to try to get it down was almost alarming at times, until I figured out it rarely went higher than 7.8 when left alone.

I'll have to look through my pics and see if I have some for the concrete or get a few shots tomorrow, will post back with those.

 

[PoolStored]

I had let the pool run for a few days before that testing

Great.

I was wondering why I not able to build chlorine levels with the generator

Generator will work, but not clear, from your signature, what cell you have...an undersized cell may not raise FC fast enough. Might use liquid chlorine to raise FC, and cell to maintain.

Will continue with my planned sand refill, already had some on order at ACE.

Great.

dry acid

Please suspend the use of dry acid. It adds Sulfates, which corrodes metals and concrete, especially SWGs. Use Muriatic acid to lower pH.

 

[HermanTX]

The amount of dry acid I put in last year to try to get it down was almost alarming at times, until I figured out it rarely went higher than 7.8 when left alone.

Most manufacturers of SWCG do NOT recommend the use of dry acid with a SCWG. As indicated by @PoolStored it also has other unwanted consequences.

 

[bc1080]

Thanks again, especially for info on the dry acid! Something I never thought about checking about, just started getting the acid at the local home store. Will switch over to muriatic when necessary to add more.

Our SWCG is a Hayward T15-turbocell. I assumed that with the initially low salt and CYA it was unable to produce enough chlorine to offset use and loss to sunlight. After I got the pool running, I was able to maintain/adjust chlorine with the generator. I was having to keep the generator set around 25-30% to maintain a proper FC level, and that is with the pump running 24/7.

Speaking of CYA, due to the somewhat subjective nature of the test, I have been vary wary of going too high and have kept it toward the lower end of the range. I have seen slightly different suggested ranges, one being 30-50, another 60-80, I tried to target 50-60. It was also mentioned a shaded pool can sometimes get by on the lower end of the range compared to one with heavy sun exposure.

I attached some pics of concrete crack examples. They are not that large or gapped, typical of what I've seen on a lot of concrete, settling cracks and cracks at corners, etc. It doesn't look they added many control joints, so I guess it cracked where it wanted.

 

[PoolStored]

Target 60 for your CYA and you'll be fine. It will just extend the life of the cell.

@ajw22 might have some ideas on the deck...

 

[bc1080]

Good deal, thanks again! Sorry for the long response time.
I have had a lot of trial and error time at various CYA levels, and I can certainly understand there's a sweet spot for salt cells. I've dealt with CYA being too high and too low, which required higher SWG duty cycles to either maintain a higher chlorine level or combat burn-off losses, respectively.

 

[Lake Placid]

Are you sure the pool is a sand base and not a California/hybrid style pool, or a gunite pool that was lined due to cracking in the shell or other shell issues? The lumps in the picture lead me to believe there is some shell settling underneath. Is it possible it was a gunite pool with cracks in the floor and sand was used to pad out the shell before the liner was installed? Sand washes out of the cracks and they are now exposed for the liner to be pushed into? Just spitballing here……

 

[bc1080]

Good catch in the photo, I forgot that was even in the shot, that is one of the areas that has me a little worried (a couple more areas in these pics). When we replaced the liner the guy who did it said it was a sand bottom, it looked like it to me but I didn't get in there and really check it out and didn't know much about it at the time (I attached a pic from mid-install). The contractor said in his local experience, older pools with sand bottoms are generally best to leave sand, trying to convert to a hard surface can sometimes lead to difficult to fix problems later on. The installers did rake and re-grade the sand prior to putting in the new liner, but we also got a massive thunderstorm about 2 hours after the install was done while there was barely any water in the pool, so not sure if that could have created issues.

 

[Lake Placid]

Your pictures are worth a thousand words. Sand bottom, runoff likely moved the sand…probably water moving around the metal walls before the liner was locked in place and channeled it. Best guess.