High chlorine levels and Ph test accuracy; and high CYA too

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T

TonyAl

0
Jul 17, 2013
9
Phoenix, AZ
I just moved into a house in Phoenix Arizona with a 13,000 gallon in-ground pebbletech pool and I'm learning how to take care of it, been reading a lot of info here on the site. I'm pretty sure I need to drain and refill but can't do it until the weather cools down. I'm wondering if there is anything I should adjust in the mean time. I've been using The Pool Calculator to determine goals, and have been trying to keep my FC high because of the high CYA. The CYA result was obtained by diluting the pool water with distilled water 4:1 and then multiplying, not sure how accurate that is. I have the K-2006 kit, and current levels are:

FC: 32.5
CC: < 0.5
Ph: 7.2
CYA: 400
TA: 130
Calcium Hardness: 750
Water temp: 93 F

Also, with the levels being so high on some of these tests, will it affect the accuracy of the other tests? For example, I read that high chlorine will affect the accuracy of the Ph test but I don't know how to compensate for it. I've never seen the Ph test result above 7.4, and it will keep going lower each day unless I keep the aerator on. I've been trying to keep it around 7.2.
 
Re: High chlorine levels and Ph test accuracy; and high CYA

Welcome to TFP!

Really the only interaction is the high FC resulting in higher than true pH. Everything else should be accurate.

You have to lower that CYA. Do a search for the tarp method as a way to replace water while keeping the pool full.

Why is your pH dropping? That is not normal. Are you using only Dichlor and trichlor pucks?
 
Re: High chlorine levels and Ph test accuracy; and high CYA

Thanks for the quick response! How should I compensate for the FC level in order to get an accurate Ph measurement?
When I first moved into the house, about 6 weeks ago, the pool had zero chlorine. I hadn't found out about TFP yet, so I went to the pool store and did what they said for a couple weeks: many bags of different shock powders, two floaters completely full of trichlor pucks, and constant pump running. I finally found the TFP site and started using 10% liquid chlorine to boost FC as needed, but still have one of the trichlor floaters to maintain the FC level. I plan to get rid of it after I get the water replaced and the CYA lowered, but for now the damage is done. If I keep the aerator on 10 hours a day the Ph stays at 7.2 – 7.3.
 
Re: High chlorine levels and Ph test accuracy; and high CYA

You can not "fix" the pH test. You have to wait for the FC to drop below 10ppm.

Stop using and Dichlor and trichlor and the pH will not drop any more.
 
Re: High chlorine levels and Ph test accuracy; and high CYA

I must say.... WOOWIEE!! That's some high CYA you have there!!

Can I ask why you are waiting until the weather cools down before you do a water change?
Is it simply because the heat is just unbearable, so you're trying to keep from doing any major work in the sun? :sunny: Which I can tooootalllly understand!!!

David Spade once, jokingly in his usual sarcastic way of course, said: "Phoenix Arizona, Valley of The Sun??... More like The Surface of The Sun!". :laughblue:
LOL, so true! At least to this Oregonian. :mrgreen:

That aside, is there another "technical" reason?
BTW, here's the link to the successful "Tarp Method" thread.
foreclosure-swamp-in-pensacola-florida-t54326-40.html#p449932
Lots of photos and info on the tarp, plus the whole process.

PS. When you diluted the CYA test, did you only dilute the sample part and did so "before" adding the reagent? IE. You still used only 50% reagent when you were done diluting.
What number did you get with the dilution where the dot "fully" disappeared and what did you use as a multiplier?
Last question...
Did you do it outdoors with your back to the sun and the test tube @ waist level?
If not, re-do the test, but check here 1st to make sure you're doing the dilution right.

That stuff "dilution ratios" makes my head hurt. :hammer:
Hang in there, you'll get her whupped into shape with our help and this board's collective knowledge in NO TIME FLAT!! :cheers:
 
Re: High chlorine levels and Ph test accuracy; and high CYA

I was waiting until the weather cools down to drain it because the pool store dudes said it would damage the pool to drain it if the temperature was above 80 degrees. Is it not true?

I diluted the CYA sample before adding the reagent. The first CYA test I did showed 100, second test I diluted 1:1 with distilled water and it showed 100, third test I diluted 2:1 and still showed 100, fourth test diluted 3:1 still showed 100, fifth test diluted 4:1 showed 80. I have no idea what the error introduced by this much dilution would be but I assume it is significant.
 
Re: High chlorine levels and Ph test accuracy; and high CYA

As Jason mentioned, if you use the "tarp method" to replace your water, you should not incur any damage to your pool.

For the tarp method, basically, you buy a tarp that is about 20 feet wider and longer than your pool. Put the tarp over your pool. Drain the water that is beneath the tarp and add fresh water above the tarp. Once the tarp gets to the bottom of the pool, your pool will be full of mostly fresh water.
 
Re: High chlorine levels and Ph test accuracy; and high CYA

You can do a drain/refill without lowering the pool, (and without a tarp, but not as efficiently) provided your water cost isn't unreasonable.

Begin a siphon at one end of the pool with the siphon (garden hose) extending only about a foot in depth.

Simultaneously, begin to add refill water down near the bottom of the pool and at the opposite end.

Adjust the refill flow to match the outflow from the siphon

To an extent, that will keep the pool and refill waters from mixing and you should be able to get your CYA reasonable fairly soon without extensive waste of new water.
 

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Re: High chlorine levels and Ph test accuracy; and high CYA

These are some good ideas. The tarp looks pretty crazy, not sure I can do that one but Dave's method with the two hoses seems reasonable. Is the pool store guy right when he says I will damage the pool if I drain it when the temp is above 80? Also, there is someone in town with a reverse osmosis machine that quoted me $400-$500, is this reasonable?
 
Re: High chlorine levels and Ph test accuracy; and high CYA

Reverse osmosis may be viable where you live as it will lower both CYA and CH, how important this is depends on how high your CH is in your fill water, high fill water CH is a common problem in your entire region and based on your test results your CH is also getting to the upper end of its managable range. At this point RO vs Water replacement is a simple matter of economics, how much would 13,000 gallons of water cost you, either trucked in or filled from your tap. I am not an expert on pebble tec, I do know you should not let any plaster finish dry out, however with only 13K gallons it should be possible to do most of the drain / refill during the evening / night hours. Even the smallest gasoline powered water pump (clear water or trash pumps, etc.) will flow well over 100 gpm with 250 - 300 gpm being typical, these can often be rented for under $50 per day (Harbor freight even sells a cheap 150 GPM model for around $180) , and a 250 GPM model can empty your pool in under an hour (assuming you have somewhere to drain the water too. A typical high quality 3/4 inch garden hose will flow between 5 and 12 gpm depending on pressure (a cheap 1/2 inch hose will flow about half that), using 10 gpm for a typical single hose your pool should be filled more than enough to cover the bottom even if you have a deep and shallow end in 5-6 hours of fill time available even if your start late in the evening. (6 hours at 10 gpm is 3600 gallons)

Ike

If your not in a rush, you can always use some of your pool water to water plants you may have, etc. I doubt you have a lush green yard to water, but you may have something you can use it on rather than simply waste it by dumping.
 
Re: High chlorine levels and Ph test accuracy; and high CYA

I took the floaters out about a week ago and have been using 10% liquid chlorine to maintain FC since then. The Ph test is showing 7.4 and it is no longer dropping as it was with the floaters in, so it must have been the acid from the pucks that was causing the Ph to drop all the time.

I am adding about 64 oz of the 10% chlorine each day to maintain FC of 30, so 2 gallons a week. This seems more expensive than using the floaters. After I drain and refill, will it require less chlorine to be added each day to maintain FC?
 
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