Indoor Pool Chemistry Problems

[summersatthelake]

First of all, I have a salt water pool at home (my second year with it) and have 0 problems balancing it. I am a Realtor and I represent a development and it has an indoor pool and an outdoor pool and I have been balancing those as well. I haven't had any problems balancing the outdoor pool (pebblesheen,3" pucks) but the indoor pool is giving me fits.

Indoor pool,19,000 gallons, sand filter, pebblesheen, 3" triclor pucks, pump runs 24/7, auto-cover is closed most of the time as it has only been swam in a couple of times over the winter, pool was new last year. Everything stayed fairly close to balance until the last 3 weeks or so and now I am not sure where to start.
I was testing with a smaller test kit but the Taylor K-2006C came in today and ran a full test.

FC/CL--Sample turned pink after adding R-0870 and after 50 drops of R-0871 it was still pink
PH--7.4
TA--After adding regents sample turned blue (not green) 20 drops of R-0012 turned it yellow (not red) and after 70 drops it was still yellow
CH--After adding regents sample turned light pink (not red)after adding 5 drops of R-0012 sample turned light purple and was still that color after 50 drops
CYA--Level doesn't reach the scale..can't see dot after 25 drops so best estimate is 250-300?

I also tested with a Aquacheck test strip and came up with
FC-10+
Total Chlorine--10+
PH--7.8
TA--180
CH--1000+
CYA--300+

Let me know if any more information is needed and any help is greatly appreciated.


BTW...the pool water is crystal clear

 

[JasonLion]

The TA test going blue/yellow instead of green/red is normal when the FC level is that high. You are looking for a color change, not a specific color.

When the CH test turns purple you are getting what is called a fading endpoint. You can usually prevent this by adding five drops of titrant before adding the buffer and indicator. Remember that the five drops of titrant count towards the total. A fading endpoint is usually caused by metals in the water. It can also happen when you go too quickly through the test. You want to swirl the sample for a good 15 to 20 seconds between drops of titrant.

The extremely high FC level invalidates the PH test. I am concerned that the PH is possibly very very low, because high FC levels usually make it read way above actual. However the very high TA level tends to argue against that.

You should never use trichlor on an indoor pool.

The indoor pool is far away from balanced. If it was in balance three weeks ago, then someone else has been adding chemicals, and in large amounts. If CH is really near 1000, you are very close to having scaling problems.

 

[duraleigh]

The indoor pool is far away from balanced.

Jason is the master of understatment. If your numbers are anywhere near correct, and you wish to balance that pool correctly, you have no choice but to replace about 80% of the water.

On top of what Jason mentioned, your CYA is completely excessive. The only way to reduce CYA and CH is to drain and refill.

If the pool was fine 3 weeks ago, there has been a huge testing error. Review your test methods and/or possibly test again. It would be close to impossible to go from normal to those levels in three weeks.

 

[PaulR]

For very high CYA, you can dilute the pool water with tap water; half-and-half, then test and double the result, or 1/3 pool 2/3 tap and triple the result if it's really high.
--paulr

 

[summersatthelake]

Thanks Jason,
The triclor is from the original supply the pool builder left when the pool was built..I read on here not to use triclor and asked them about it and they just laughed.
My previous test kit didn't test for CYA or CH so I never really had those numbers until today. There is a maintainence person here that vacuums and cleans the pool but doesn't test it...he might have added chems and I will check. It probably started about 4 or 5 weeks ago now that I think about it closer.
I'll test again tomorrow but it looks like a partial drain might be the answer.

 

[summersatthelake]

I drained about 75% of the water on Saturday and then refilled and let the water circulate for over 24 hours and just tested a few minutes ago. I have gotten used to the Taylor K-2006 testing kit a little more and am pretty confident that the results are fairly accurate. I have also checked my pool at home (saltwater) and the outside here (chlorine/pucks) and the CYA was well within reason..I never did a CYA test before as I didn't have the correct kit.
The free chlorine is still really high
FC 10.6
CC .05
PH 7.4
TA 270
CH 300
CYA 30

 

[JasonLion]

FC is a little high. You would like it to be between 2 and 6, but it won't cause any real problems at 10. FC will come down on it's own, though it may take a while.

Your TA level is a little high. Keep an eye on the PH and if the PH is going up annoyingly quickly you should lower TA.

For an indoor pool, I suggest trying to keep CYA between 20 and 30. If you are still using trichlor, you will need to get into the habit of regularly replacing water.

All of the other levels are alright.

 

[ideliver]

Unless the pool gets sun...there is no need trichlor...and it sounds like you have a light bather load...i suspect your FC use will be less than 0.5 ppm/day...this should be easily maintained with a few cups of bleach (use poolcalculator.com)

in comparison...my outdoor pool needs about 3 to 4 ppm/day...full sun/uncovered

 

[summersatthelake]

It appears that the consenus is to not use trichlor in an indoor pool. I read and re-read pool school and water chemistry and was having a really hard time grasping everything until I was able to recently start running a full test with the K-2006...it makes alot more sense now but I still have a ways to go.

I think we are going to go with bleach for the indoor pool and yes it gets a really light bather load.
I guess that the other option would be a SWG. The PB said that they would never recommend a SWG for an indoor pool...but they also installed the trichlor puck feeder and recommended 2 lbs. of Cal Hypo shock weekly.

 

[PaulR]

It appears that the consenus is to not use trichlor in an indoor pool.

Well.... you'd think the same would be true for a spa (thick opaque cover 99% of the time) but actually 20-30ppm CYA is helpful just because of the chlorine buffering effect. With zero CYA you only need about 0.5ppm FC but that's hard to do consistently. With some CYA and the appropriate FC level you get good sanitization plus you have some leeway with the exact FC level.
--paulr

 

[JasonLion]

The conventional wisdom for indoor pools is to never allow any CYA into the pool under any circumstances. Around here we recommend CYA between 20 and 30 for indoor pools. No one, using any system I have ever heard of, ever recommends using trichlor in an indoor pool.

Hot tubs are a completely different situation. The water is easily replaced, so CYA isn't much of an issue. Some people recommend using straight dichlor and just assume you will be replacing the water frequently.

 

[PaulR]

I'm not recommending straight dichlor or trichlor; I'm saying in an indoor pool, CYA 20-30 will be as beneficial as it is in a spa, and you get there the same way as you would in any other situation (dichlor/trichlor temporarily, or straight CYA). Although it might be hard to get that understanding out of what I actually said last night.
--paulr