White/cream stains

[algonquinforestpool]

Hello! I am a brand new salt water pool owner (in Canada) and trying to quickly get up to speed on how to manage a pool (and two busy little boys). I've had the pool about 1 month now and no major issues except for a very slow but increasing build up of this white/cream stain in a strip around almost the whole pool, right at the point the vertical walls starts to slope down or meet the floor. I have the water tested weekly at the pool store and the only continuing issue is high Ph (7.8) so I'm regularly putting in a PH- product but haven't gotten it below 7.6 yet. Chlorine levels are on the high side but good. Hardness was low and we added Calcium. Salt was low and we've added 6 bags of salt so far, 1 more to add.

If I try to scrub the stain in one spot for a long time, it seems to lighten slightly but I can't get much force using the pool brush from above the surface. I admit that while I've been vacuuming every week, I haven't been brushing the sides regularly. It's not slimy at all, maybe a bit gritter but mostly just feels the same as the rest of the liner.

They tested for metals in the last water test based on what I told them about this and it came back negative. Any ideas what I'm dealing with? I poured in a bottle of a scale remover around the edge yesterday but didn't do a thing (or do I need to wait longer?).

Thank you for any help!!

 

[JVTrain]

First things first. Here on TFP, we generally do not put much faith in pool store test results. Frequently, they appear to be very sophisticated devices with that give results to the hundredths decimal place and emit fancy print outs telling you how much stuff you need to buy from the pool store. TFP methods are based on reliable, convenient and inexpensive testing at home, by the pool owner. Pool store testing is worth exactly what you pay for it. Nothing. Check out the Pool School - Test Kits Compared for the test kits that will have everything you need. The TF-100 is the best home owner test on the market, but because you are located in Canada, it's difficult to get one. The Taylor K-2006 test kit is your best bet. They are more expensive in Canada than the US, but it's your best option.

Once you have a test kit and can post a full set of test results, you'll be able to get better help here from us and take control of your pool without ever setting foot in the pool store again. Check out ABCs of Pool Water Chemistry and Pool School - Recommended Pool Chemicals and you'll see that our methods are not the same as the pool store and most everything you need for your pool can be gotten for cheaper than the pool store at places you probably shop already.

 

[algonquinforestpool]

Thanks! I've gone through what you recommended, very helpful. Glad to know I don't have to rely on the pool stores! Fortunately (and surprisingly!), we have a Taylor K-2006 already! My husband bought it for the hot tub in our previous house but he didn't know it would work for a salt water pool. Glad to hear it does!

So I tested with the kit and can't say I'm 100% confident I did it all correctly but here are the results:

FC 5.2 ppm
PH 7.7
TA 130
CH 150
CYA 33

Last week's pool store test result showed my CYA at 70 so I was surprised by my result (but I used a different pool store the week prior and their result was 38 so much closer to mine). Can it change so much week to week?

Based on the Water Balance for SWG post I found, it seems my alkalinity is too high and CYA is too low right? Can these cause my stain issue?

 

[JVTrain]

CYA does not change that much in a week. It can drift downward over time due to backwashing or other draining followed by a refill but CYA goes nowhere in pool water except for special circumstances.

I don't see a problem with your results that would lead me to believe you'd have scaling from the pool water being out of balance. The only way you would have scaling with those numbers is if you were routinely letting your pH climb above 8.2 for long periods of time.

Your TA is a bit high, but just maintain your pH between 7.2 and 7.8 and each time you add acid to lower pH, the TA will come down over time. Sounds like you're using a powdered pH reducer (sodium bisulfate?) How often are you adding? Powdered pH reducers are convenient but they can build up sulfates in the pool. Are you brushing the area where you add the pH reducer after adding? You could have sulfates crystallizing causing the rough area but this would be uncommon in a new pool. I would recommend switching to muriatic acid for pH reductions. It's a bit more hazardous to deal with but does not have the side effects of dry pH reducer.

I can't tell you if your CYA is too low or too high because I don't know how you're chlorinating the pool. Please fill out your forum signature to include your pool details and you'll get better advice.

 

[algonquinforestpool]

Thanks again. I've worked at piecing together the details for my pool and added them to my signature. The pool is not new but I am new to pool ownership (new house came with the pool).

I am using a powered pH reducer, I spread out the application over a few days and spread it evenly around the deep end. I haven't been brushing after but started to yesterday after reading your post. But I will switch to muriatic acid for future thanks.

The creamy (actually kind of yellow) stains seem to be getting worse and more in the shallow end too. But still staying in a ring around the perimeter of the pool. Water looks great though. Not sure if it's related but I can smell chlorine when I walk outside which I couldn't before (this is new in the past couple weeks). Given my stats, perhaps I can reduce my salt cell chlorinator down a bit? It's currently running at a 3 out of 5.