Water test results?

[andy]

I am new to the forum and would like opinions on what I may want to do with my water.

Pool info:
21,000 gal Fiberglass
Indoor with auto cover that is on all the time
Auto Pilot Total Control System(salt/chlorine generator)
Sta-rite Mod Media 3 Cartridge Filter
Pool is kept at 83 deg and heated to 88+ sometimes

Test Kit info:
Taylor K-2006C service complete (FAS-DPD chlorine)
Taylor K-1766 sodium chloride (salt water)

Auto Pilot Total Control reads:
ORP 659 high
PH 7.17 low
salt 3000

Taylor kits read:
FC .2
CC .8
PH 7.1 (says add 2lb soda ash)
Alkalinity 120
Calcium Hardness 400
CYA (I couldn't get a reading because the solution never turned cloudy)
Sodium Chloride 3000

I've been adding ProTeam Metal Magic on occasion to help with the brown stains.

Problem....I have some BLACK spots/stains appearing on my water line tile grout(silicone) as well as my perimiter fiber optic cable. I can't seem to get them to clean off.

Any suggestions are appreciated! Thanks, Andy

 

[duraleigh]

Hi, Andy,

Welcome to the forum. Indoor pools are such different animals that I can't supply the advice you need. There are others here on the forum who will be along soon to comment. They are indoor experts and, while I've read the threads,I cannot recall specific info that may be helpful to you.

 

[JasonLion]

Welcome to TFP!

To have the ORP reading you have with that low a FC level your CYA level must actually be very close to zero. That is fine and is the traditional recommendation for indoor pools. However it is worth noting that Chem Geek has been recommending using some CYA in indoor pools, contrary to the traditional approach.

Your PH is low and TA is a little high, which is kind of surprising. Running the SWG should raise the PH and lower the TA over time. I would suggest letting TA drift down to perhaps 70, which is likely to take a while. If you haven't intentionally lowered the PH recently it is probably a good idea to raise it a little, say to 7.4, to reduce potential eye irritation. I would use borax to raise the PH to minimize any increase in TA.

Your CC is high. Ideally, you don't want to have CC above 0.2 (when measuring by 0.2s, 0.5 when measuring by 0.5s). You might want to shock the pool until CC comes down. Shock level is perhaps 2 for this pool. CC can be complex to deal with in an indoor pool. Because of the Total Control system you can't use non-chlorine shock, which is one of the traditional remedies for indoor pools.

Try rubbing a stain gently with a couple of crushed vitamin C tablets in a sock and see if it changes color or goes away. Also, while shocking watch to see if they change in appearance. That will help narrow down what might be causing them.

 

[andy]

Welcome to TFP!


Your CC is high. Ideally, you don't want to have CC above 0.2 (when measuring by 0.2s, 0.5 when measuring by 0.5s). You might want to shock the pool until CC comes down. Shock level is perhaps 2 for this pool. CC can be complex to deal with in an indoor pool. Because of the Total Control system you can't use non-chlorine shock, which is one of the traditional remedies for indoor pools.

Try rubbing a stain gently with a couple of crushed vitamin C tablets in a sock and see if it changes color or goes away. Also, while shocking watch to see if they change in appearance. That will help narrow down what might be causing them.

What should I use to shock the pool? Should I just put the Auto Pilot on boost? Also, how many hours a day would you suggest I run the pool? I have the control set to run 6 hours a day now.

 

[JasonLion]

I would shock with bleach. When shocking you want the FC level to go up as rapidly as possible, which is best done with something other than the SWG. Also, bleach will give you more precise control over the final FC level. When running without CYA it is important to not let the FC level get too high. FC can easily get way too high if the SWG is run on boost mode (or in percentage mode) on an indoor pool.

Pump run time is mostly really a subjective issue. You want to run for the shortest amount of time that keeps the water looking good and gives the SWG enough time to maintain the FC level. I would split the run time into two blocks and experiment with shorter and longer run times for a week at a time to see if you can detect any change in the water appearance. The common rule of thumb is to run the pump long enough to turn over the pool once per day, but unless you have a flow meter that can be tricky to figure out, and in the end how the water looks is what really matters anyway. Run times that are too short will result in a subtile loss of water clarity or reduce skimmer efficiency enough to give you some visible effect.

 

[andy]

After weeks of trying I can not get my CC to lower. I've breakpoint chlorinated the pool twice raising the FC up to 8.4+ while the CC was .8-

Today the test results read:
FC .6
CC .6
PH 7.3
TA 120
CH 350

One thing to note is each of the two times I've added 2gal pool shock, when I check the pool a couple days later.....I have ALOT of fine sandy like stuff all over the bottom of the pool. I've vaccumed it up each time. Any idea what this is????

Again this is an indoor salt pool that has the Autopilot Total Control system which controls the chlorine and ph on its own.

Thanks, Andy

 

[JasonLion]

One thing to watch out for. If your CYA level is really and truly zero you don't want to bring FC above 5. On the other hand if your CYA level is above 2 (impossible to measure below about 15 unfortunately) you don't want FC going below 1. My guess is that your CYA level is zero, since the AutoPilot Total Control system wouldn't normally allow FC to go that low unless CYA was close to zero. So you should be careful about having FC too high (some risk above 5, lots of risk above 10).

This is a classic problem with indoor pools. Sunlight really helps keep CC down. Also, the classic fix, using MPS to prevent CC from forming in the first place, can't be used with the ORP controller in the Total Control system. Unfortunately that exhausts my indoor pool knowledge. Hopefully someone else with have a more useful suggestion.

 

[chem geek]

First of all, I would get some Cyanuric Acid (CYA) into the water, though it doesn't have to be very much. 20 ppm would be fine. Then you would target an FC level of around 2 ppm, but you have to make sure to not let the FC drop lower (your current FC of 0.2 ppm is way too low once you've added CYA to the water). Right now, if the CYA is truly zero, then the combination of chlorine (FC) and high salt levels can be very corrosive to stainless steel (and, to a lesser extent, to other metals). This post at The Pool Forum describes one user's indoor SWG pool with no CYA and 3-5 ppm FC (his initial .3 ppm was a typo). You mention brown stains so I wonder if that's from metal in your fill water (you should have it tested for iron and copper and possibly manganese, though brown stains are usually iron) or if it's rust from metal exposed to your pool water.

Also, from my wife's experiences with a commercial indoor pool with no CYA and 2 ppm FC vs. our own outdoor pool with 3.5 ppm FC and 30 ppm CYA has noticeable degradation of elasticity in her swim suits (and rougher skin and hair) in just one season of use in the indoor pool while the outdoor pool has no such problem. Essentially, without CYA, you are overdosing your pool with disinfecting chlorine.

I've also done some breakpoint calculations that show that there are more disinfection byproducts, DPBs (the nasty ones of dichloramine and nitrogen trichloride) formed if there is no CYA due to the higher disinfecting chlorine concentration. Water treatment plants that use chlorine try to dose with the smallest amount of chlorine to avoid such DPBs.

As for the Combined Chlorine, I think the secret to lowering it in your case is to keep the pool uncovered for a while after you shock with chlorine. I would first add the CYA to 20 ppm and then just shock to an FC level that is no more than 40% of the CYA level (8 ppm FC if 20 ppm CYA). Be sure to leave the cover open and circulate the air as best you can for one hour. My calculations show that at the 40% shock level, breakpoint is about half done after 10-15 minutes and about 90% complete after 30-40 minutes. Even at the more normal 10% of CYA level, breakpoint should be about half complete after 40-60 minutes and 90% complete after 160-210 minutes. So it is important to keep the pool uncovered after using it to give the pool a chance to "breath" and release gasses (mostly nitrogen gas and some carbon dioxide).

I think that between the SWG cell superchlorinating some of the water and having the pool be uncovered a little more, that you will be able to control your CCs a little better. Also, with some CYA in the water, you might not get the brown staining you are seeing and should have a much better balanced pool.

The only other suggestion would be to lower your TA level a little and let you pH go up a little. If you wanted a pH target of 7.5, then you would need to lower your TA level to around 80 ppm (even after adding 20 ppm CYA). Your currently lower pH doesn't help with the metal corrosion either, though it isn't bad (i.e. it isn't below 7.0). You can lower your TA level by following the procedure in this post on The Pool Forum and I explain why this procedure works in a table in this post.

Richard

 

[waste]

Andy, welcome to TFP :-D :!:

Jason and Richard have (of course ) given you the 'why's' of adding some cya to your pool. I'm gonna tell you the 'hows' of doing it

Cya addition cab be tied to the salt addition you did when starting the system. To get to 30 - 40 ppm cya, in a pool that runs with ~3000 ppm salt, I add 1 lb cya per 100 lbs salt. For your 21000 gal pool, I think that 2 - 2.5 lbs of cya would get you to where you want to be, to keep the "evil chloride residuals" at bay and prevent the swimsuit destruction that Richard mentioned.
Adding the dry cya is another thing; you could add it into the skimmer but for your cart filter, the acidity of it would harm the cells! With your fiberglass pool, your could add it dry to the water itself, but the acidity of the chem could cause some with your pool surface. I'd hang the cya in a pantyhose knee-high in front of a return while the pool is running and remove it when the pool isn't running (you can put the cya packet on a plate when it's not dissolving ) It will take a few days for the packet to dissolve, and ~a week for the dissolved cya to clear the filter.

Others will 'chime in' about what I just suggested -- but I feel that this is the proper way to do it :-D