Pool blues (greens?)

[deejor]

Hi all,
First time poster although I've been lurking on the site scouring for info over the last year or so (alot last summer ). We are renting a house in Tempe, AZ and really enjoyed the rather large diving pool last year, until it turned green that is. Knowing next to nothing about pool maintenance and following the vague directions of our landlord I kept the floater filled with tablets and shocked the pool here and there with the powder shock, threw in some clarified and algaecide for good measure and got it turned around a couple times from a slight algae bloom. Basically we spent a ton of money.

Then it went deep green, probably due to high CYA and inadequate chlorine levels. Having read the forums here a bit I realized that my test strips were not going to cut it and that this was more complicated than I thought. I was getting conflicting information from everyone I talked to, friends/landlord/poolstores. I was pretty convinced that I needed to purchase one of the two recommended pool kits and tackle the situation armed with chemical knowledge of our pool and online support. Then I talked to the wife...

She talked me out of buying the kit, figuring that we might not still be here after our 1yr lease and that it was possible that I would be unable to fix the situation even with the proper tools. The pool service was only x amount per month and they would provide all those expensive chemicals and then for sure we would be able to swim the last few weeks of the summer. Right?...wrong!

The pool service shocked the pool with massive amounts of chlorine. Came back and shocked it again 2 days later. It lightened slightly and then went full green again. We paid for the spider gasket to be replaced after they found it was tattered and were sure that would fix the problem. Wrong again. Their next suggestion was to drain the pool completely which the landlord balked at fearing it would damage the plaster. We agreed to drain the pool about half way and then refill it. The pool service was able to get the pool back to clear but by that time it was a bit cold to swim.

Pool stayed nice and crystal all winter long (of course) and when it started heating up again and after we signed another 2 year lease I vowed to tame the beast before it turned green this time. I purchased a TF-100 and bought 6 large bottles of bleach to start working with. I had a gallon of the 12% liquid chlorine from the pool store from last year but that sat in the pool shed so I'm not sure how effective it was. I've been adding bleach every 2nd evening and the chlorine levels are jumping up to the 5-10ppm reading on the small test kit (at least 30 mins after adding to pool). The levels are dropping off to 0.5-1.5ppm on the second day which i realize is not good but so far the pool has stayed crystal clear.

Anyway here are my stats:

Pool size: ~20,000 gal
Sand Filter
In ground
Plaster
1HP pump (i think) and 15GPM/ft^2

pH - 7.8
TA - 150
FC - 1.5 FAS/DPD (1hr after ~90oz of 6% Clorox reads 5-10 range on the K-1000)
CC - 0
TC - 1.5
CH - 440
CYA - 30

I was pretty pleased with these numbers, but I'm imagining that when the temperature gets up there that I'll be burning off chlorine pretty fast. I'll go through a 182oz bottle every 2 days probably? Maybe thats normal. I know right now its pretty much all gone after two days. I probably need to add it every day to be safe. Would a bit more CYA help with keep it around longer? I've added some pucks to the floater basket figuring that might help with keeping the chlorine levels up but it didn't seem to make any difference at all.

The TA seems a bit high also. Not sure if thats a problem or not.

I guess I'm looking for some reassurance that I'm on the right track and some advice about possible issues going forward. Appreciate any and all inputs.

Thanks!

 

[PaulR]

Welcome! You are very close to being in complete control of the pool. A few things do jump out at me, but they should be straightforward for you to take care of.

Your pH, TA, and CH are all high, which puts you at risk for calcium scaling.
Your CYA is on the low side for such a sunny climate.
Yes, you probably do need to add chlorine every day or two; that's the nature of using bleach.

But, these are all relatively easy to take care of. First off, keep your pH in the 7.2-7.5 range; that will seriously reduce the risk of scaling. Because of the high TA, the pH will almost certainly keep trying to climb back up; just keep after it with muriatic acid. Over time the acid will lower the TA as well, and the pH won't rise as fast, and the lower TA will help reduce scaling risk as well. If you want to hurry that process along, check out Lowering Total Alkalinity. If you do that, shoot for a TA that's under 100.

Second thing, for such a sunny climate your CYA is on the low side. I'd suggest bringing it up to the 50 range. This means you'll need to maintain somewhat higher FC levels, but your total chlorine use should go down.

This is a situation where trichlor tabs are actually a good thing to use. They are acidic (will help you manage the pH and TA) and add CYA (although somewhat slowly). Assuming you have 8-oz tabs, each tab will add about 1.7ppm CYA, so load up the floater (4 at a time if they fit) and keep it loaded until you've used around a dozen tabs. This might well not maintain your FC and you'll have to supplement with bleach. Get used to it, after the trichlor is done then you'll be using bleach all the time!

Let's see, what else. When you talk about "5-10 on the K-1000" I think you mean the yellow matches the top color block; that indicates TC 5. The "10" you see next to it is for testing bromine (notice the little "Br" at the top of the column) which you basically never see in a pool. So you're saying the TC is 5.

Because the chlorine level keeps bouncing up and down, it's possible you have a low-level algae infestation, but it's more likely the sun is nailing it. You can do the Overnight FC Test if you're worried about algae. (That would mean taking the floater out for the night.)

So enjoy! You've come to the right place.
--paulr

 

[PaulR]

Forgot to mention the Chlorine/CYA chart, use that to figure out your target FC level based on your CYA. So far I think you've been lucky, for CYA 30 you should shoot for 4-5 when you add chlorine and not let it drop below 2; looks like you've been reaching 5-ish and dropping to maybe 1.5. Make testing part of your daily routine until you get used to how the pool behaves, and you should be fine.
--paulr

 

[frustratedpoolmom]

You are really close! Great job on taking total control.

I would follow the shocking process to the end (which you haven't completed-sounds like you still have some organics consuming the chlorine).

So First, lower the PH down to 7.4 and resume shocking the pool:
Shocking Your Pool
Overnight FC Loss Test

After the shocking is complete, let the FC drop down to your "target" for your CYA level (refer to the chart) -
And then just use trichlor tablets until your CYA gets to 50... test CYA level every 3 weeks or so while using trichlor.
Monitor your PH and FC daily and make sure you are at the recommend level, monitor the TA weekly.

Once you hit 50-60 on the CYA level switch to daily bleach additions, and this will end up taking you about 5 minutes a day .

At this point you I predict you will be fairly confident in the processes and in total control of the pool... but post back if any further problems develop.

So just holler if any of this advice is not clear or you have a question about anything.

 

[lborne]

Don't trust that chlorine that was sitting in the shed all year. My first pool mistake was accepting a jug of chlorine from a friend who did not need it because they went to a salt system. It was over 2 years old and I did not have my test kit yet. Had algae in my pool 2 days after filling it.

 

[PaulR]

Right, the stuff in the shed. It won't actually be harmful, but it's probably down to about 5% by this time, possibly less depending on the temps inside the shed. It would be okay to dump it in the pool just to be rid of it.
--paulr

 

[deejor]

Hey thanks for all the feedback guys. Good to know I'm not too far off here.

I'll get started on lowering the TA/PH tonight and then shock the pool once I've got that where it needs to be.

I have some muriatic acid that I bought last year along with the liquid chlorine. Guess where it's been sitting since then... (shed). Does muriatic acid lose its potency or become otherwise unusable for its original purpose when exposed to heat?

 

[frustratedpoolmom]

The MA should still be ok.

 

[deejor]

Looking good so far. TA down to 120 and PH at 7.5. Added 2/3 gal of MA last night and it was at 7.2 after 1hr. Put the rest of the gal in tonight and left the fountain on for tomorrow.