High CYA -- water change advice

[rob42]

I am a newbie trying to wrangle the pool of a house I just bought. The pool *looks* great, BTW, for some reason. Perhaps it's too toxic for algae to grow.

I had been testing free chlorine and ph with the daily kit while doing the move, and CYA only with a test strip. So, what I thought I knew was that pH was low and CYA nearly non-existent. I kept adding soda ash with no apparent improvement, and must have overdone it in the last round, because now the pH is high, the other tests are now suddenly working, and CYA is "drain the pool" high!

From the pool store's water analysis (vinyl pool, ~17,000 gallons, ~82 deg F):

Free chlorine: 5.8 ppm
Total chlorine: 6.8 ppm
Combined chlorine: 0.96 ppm
ph: 7.8
Total akalinity: 157 ppm
Calcium hardness 7 ppm (yes, 007)
Cyanuric acid: 129 ppm

I confirmed enough of this, including CYA, with my own test kit to be comfortable with the truth of it.

So, ... bummer. It appears that there is no point in doing anything until I drain and refill a lot of water, correct? I have a vinyl liner, and I don't want it to get sloppy, so can I drain the vertical part of the pool and stop short of exposing any of the bottom, then fill and test again?

Doesn't seem like there's any point in addressing any of the rest of it until the CYA is down, because I will be testing 50% (or more) tap water next time, right?

Also, just out of curiosity, do I *need* calcium hardness in a vinyl pool? I need to add 30-some pounds to get it up to a normal range according to the pool store.

Thanks for any advice.

/// Rob

 

[borjis]

Yes do not drain too far for a vinyl or wrinkles or shifting can happen.
Generally there needs to be at least 1 foot of water in the shallow end at all times.

I have a pool near that capacity. What I did when I had to replace some
water from a metals issue, was drain about 1-2 feet of water, then top it up again.
Then run the pump for an hour or two and retest everything. If the CYA is still
too much...then do it again.

This is with a shallow end of 3.5 feet depth.

You might only have to do this once or twice. Maybe three times at most.

But first, before doing anything you should get a Taylor K2006C or TF100 test kit.

Test strips and basic drop kits are just not very accurate (pool stores are not reliable either),
but either of these two kits mentioned will give you solid, EXACT numbers so you can
have your pool water tuned perfectly.

I'd get that kit first, then test everything again and post those results.


You do not need calcium, but most of us keep ours around at least 75ppm to avoid any potential water foaming issues.
Guesstimating I'd say maybe 30 lbs of calcium up to get there, but use the proper test kit first to see what it really is.

Then use the pool math page on the site to figure how much you really need.

 

[Dirk]

+1!!!!

I wouldn't add chlorine based on what a pool store had to say about it. I certainly wouldn't be contemplating replacing water to satisfy pool store numbers or advice. Get the kit, then come on back for some good advice...

 

[ajw22]

Your numbers are not that bad. No reason to panic.

Do as little as possible until you get your own testing kit. That means maintain the FC level. That is the vital thing now. You want a minimum FC of 8 and a target of 13-15. Error on the high side. Use PoolMath and give your pool sufficient doses of LC.

PH of 7.8 is not awful high. Stop tinkering with PH unless it gets above 8. Then add MA to get it down around 7.5.

Don’t do anything with CH until you get your test kit. If you are going to drain water to fix your CYA then test your fill water and see what its CH is. You may solve part of your CH problem with the fill.

Eventually you need to do something if you have high CYA. Dont react until you have your own test results.

- - - Updated - - -

+1!!!!

I wouldn't add chlorine based on what a pool store had to say about it. I certainly wouldn't be contemplating replacing water to satisfy pool store numbers or advice. Get the kit, then come on back for some good advice...

Why not add CL while waiting for the test kit? Lets prevent algae taking hold. No harm in keeping FC up to SLAM levels. With CYA possibly at 100 that could be up to FC 39.

 

[Dirk]

Your numbers are not that bad. No reason to panic.

Do as little as possible until you get your own testing kit. That means maintain the FC level. That is the vital thing now. You want a minimum FC of 8 and a target of 13-15. Error on the high side. Use PoolMath and give your pool sufficient doses of LC.

PH of 7.8 is not awful high. Stop tinkering with PH unless it gets above 8. Then add MA to get it down around 7.5.

Don’t do anything with CH until you get your test kit. If you are going to drain water to fix your CYA then test your fill water and see what its CH is. You may solve part of your CH problem with the fill.

Eventually you need to do something if you have high CYA. Dont react until you have your own test results.

- - - Updated - - -



Why not add CL while waiting for the test kit? Lets prevent algae taking hold. No harm in keeping FC up to SLAM levels. With CYA possibly at 100 that could be up to FC 39.

Oh, I didn't write that well, at all. I didn't mean "Don't add chlorine." I meant "I wouldn't trust pool store numbers to do anything to my pool, even if they told me my chlorine was low."

Yes, do maintain FC levels while waiting for your kit. Don't be doing anything drastic, like draining your pool, until you get your own kit, your own numbers.

 

[rob42]

I do have the test kit. I did confirm most of these numbers with the test kit. The CYA was confirmed insofar as the viewing tube was obscured well before I got to 100 -- extending the scale, maybe 135.

I will try draining a couple of feet and re-filling, and do a full range of tests after that. I really just want to get some use out of the pool for the rest of the season, so long as it's safe to use. Next spring I hope to be down to one house, and will have more time and funds.

 

[Richard320]

I do have the test kit. I did confirm most of these numbers with the test kit. The CYA was confirmed insofar as the viewing tube was obscured well before I got to 100 -- extending the scale, maybe 135.

I will try draining a couple of feet and re-filling, and do a full range of tests after that. I really just want to get some use out of the pool for the rest of the season, so long as it's safe to use. Next spring I hope to be down to one house, and will have more time and funds.

Repeat the CYA test using the dilution method Step 8 here: Pool School - CYA

Then when you drain, you'll be sure to drain enough.

 

[ajw22]

I do have the test kit. I did confirm most of these numbers with the test kit. The CYA was confirmed insofar as the viewing tube was obscured well before I got to 100 -- extending the scale, maybe 135.

I will try draining a couple of feet and re-filling, and do a full range of tests after that. I really just want to get some use out of the pool for the rest of the season, so long as it's safe to use. Next spring I hope to be down to one house, and will have more time and funds.

Go use your pool. Nothing in your tests say your pool is unsafe to use.

Work your test numbers down over time.

 

[rob42]

Repeat the CYA test using the dilution method Step 8 here: Pool School - CYA

Then when you drain, you'll be sure to drain enough.

Oh, cool. That should get my measurement on to the scale. Thanks!

I don't have any kind of flow meter, so I think I will be guessing on the draining and filling. I will be too chicken to drain a whole lot in one go, so I will just iterate draining and filling until I get there. Maybe I should call the city water people.

I may be able to just siphon, but I am looking at an Everbilt submersible utility pump to give me some options as to where to direct the water (not to mention ease of use).

/// Rob

 

[borjis]

Do make sure you are around / at the house when draining. Just to make sure it doesn't drain too much.

 

[Dirk]

It is possible to exchange water in your pool without dropping the level at all. You leverage the different properties of the two, incoming water and existing pool water, either their densities or their temperatures. And depending on which is what, you pull water off the surface while adding water in the deep end, or pull water from the deep end while floating new water on top. Without the filter pump running, you can achieve a fairly efficient water exchange in this way without ever emptying your pool.

If you're interested in this, we'll have to call in the experts here, as I've never done this myself... But it's how I'll do it next time, as I would be too chicken to empty my pool, too. You can ruin a pool by emptying it, plaster or vinyl, and unless water is crazy expensive, it seems prudent to avoid doing so if you can.

 

[borjis]

Total emptying = BAD yes. I suggested a foot or two at a time...no harm in that.

But I like the water exchange idea too. Either should work.

 

[Dirk]

Not to be argumentative, or to concern the OP needlessly, but there is a thread here that describes how a guy floated his liner by dropping his water level by only a few inches. The cause was explained quite well in the thread, which showed the science behind why it happened (diagrams and all). The guy had a very high water table, and the pressure differential of only a few inches was all that was needed to push his liner up. Like way up, bad. So while there are general rules of thumb about what you can get away with while emptying a pool, you have to be aware of the possible variables involved.

The water exchange process I suggested eliminates a lot of (all?) the potential dangers of swapping water, as it doesn't alter the water level at all (if done correctly).

 

[rob42]

Not to be argumentative, or to concern the OP needlessly, but there is a thread here that describes how a guy floated his liner by dropping his water level by only a few inches. The cause was explained quite well in the thread, which showed the science behind why it happened (diagrams and all). The guy had a very high water table, and the pressure differential of only a few inches was all that was needed to push his liner up. Like way up, bad. So while there are general rules of thumb about what you can get away with while emptying a pool, you have to be aware of the possible variables involved.

The water exchange process I suggested eliminates a lot of (all?) the potential dangers of swapping water, as it doesn't alter the water level at all (if done correctly).

It would make sense to me that I could draw water from the near the surface at the shallow end, and put in water at the bottom of the deep end, then the cold water coming in will mostly stay deep. The pool water is over 80 now.

I do need to find myself a flow meter using this method, though, or I won't know when I'm done! ;-) A plan forms!

Water is $12.55 a thousand, so I should not go broke.

/// Rob

 

[s_vidden]

Oh, cool. That should get my measurement on to the scale. Thanks!

I don't have any kind of flow meter, so I think I will be guessing on the draining and filling. I will be too chicken to drain a whole lot in one go, so I will just iterate draining and filling until I get there. Maybe I should call the city water people.

I may be able to just siphon, but I am looking at an Everbilt submersible utility pump to give me some options as to where to direct the water (not to mention ease of use).

/// Rob

Rob,
Once you figure out how much volume you need to drain and dilute with fresh do some quick math to determine your drop level in your pool to achieve the gallons removed. No need for flow meter. Google pool volume calc plug in the numbers.

 

[borjis]

Not to be argumentative, or to concern the OP needlessly, but there is a thread here that describes how a guy floated his liner by dropping his water level by only a few inches. The cause was explained quite well in the thread, which showed the science behind why it happened (diagrams and all). The guy had a very high water table, and the pressure differential of only a few inches was all that was needed to push his liner up. Like way up, bad. So while there are general rules of thumb about what you can get away with while emptying a pool, you have to be aware of the possible variables involved.

The water exchange process I suggested eliminates a lot of (all?) the potential dangers of swapping water, as it doesn't alter the water level at all (if done correctly).

Good point Dirk.

My water table is several feet below the deep end and is a non-issue for me. I had not considered others that way.

Cheers!

 

[getreal720]

Not to play devils advocate or anything here, but back before I knew any better I basically entirely drained my above ground pool with a vinyl liner.... then refilled it. I didn't have any issues that I'm aware of.

Over the winter I lost probably 30% of the water in the pool due to snow and ice melting and getting into the pool and mostly the stuff forcing the cover down and pushing water out from under it. So when I drained off the pool cover, I needed to add a few thousand gallons to get the pool water level back up over the skimmer basket.


Having said all that, you are probably better off doing it like 10 to 15% at a time. No reason to try to go at it all at once.

 

[borjis]

I remember this as well growing up with an above ground pool.

The difference is that in-ground pools are WAY different than above ground. More things can go wrong for sure.

 

[Dirk]

Yes, in a quick re-read, I can't find if the OP's pool is IG or AG. His concern about how much to empty led me to believe it is IG. Which inspired my comments. Pardon if I got that wrong...

s_vidden, your comment about not needing a flow meter and determining the amount of the exchange with dimensions makes sense if the OP is going to drain and refill. If he's going to exchange as I suggested, I think he would need a flow meter, at least to get close. His water level won't be dropping, so there's nothing to measure! The exchange won't be exact, and some mixing will occur, but a flow meter would keep him in the ball park.

Good news, rob42, whether you need one or not, you've probably already got one, if you're on metered water. You can use the house meter out by the street. Impose a ban on showers, laundry, dishes, etc. Go out to the street and take a picture of the number on your water meter. Start the exchange and keep an eye on the meter for when you hit your mark. The picture is in case you forget the starting number (something I would do in like five minutes!!).

You'll be hopping back and forth to maintain the water level and eye the meter. Balancing water being siphoned out vs water coming in. Then checking the meter for your target number (determined with a little math, adding the desired gallons to exchange to the original meter read). EZPZ. Meanwhile, the rest of the family will be lounging inside because they've just been given the day off: no laundry, no dishes, no washing the car, etc. It's a win-win!!

 

[wilafur]

I've been replacing the water in my IG pool for the past 5 days to bring my CYA down significantly. Per PoolMath, I had to replace 78% of my water, or approximately 24,000 gallons.

Since the new water is much cooler than the water in my pool, I ended up adding water in the deep end and pumping water out on the shallow end (with the pump sitting on the top step). It worked out quite well and was automatic once I got the inflow to match the outflow.