Test Check

[jhm]

Hi-

I was hoping smarter people than me could comment on my test results. Here they are:

FC: 6
CC: 0
PH: 7.8
TA: 150
CH: 210
CY: 25

My PH always runs high. I'll be lowering it tonight with Muriatic Acid. The TA seems high, should I lower it? Could it cause my PH to always be on the rise?

The last two years I've had recurring mustard algae outbreaks. It's in remission now, but if the chlorine drops to around 1 on a hot day I still see it creep back.

My CYA seems to have dropped by about 15 in the last 2-3 weeks. Is that possible? I'm in SoCal, so I've gone to supplementing bleach with a floater to make sure the chlorine stays up and I'm hoping that will help enough with the CYA.

Are any adjustments in order?

Thanks!

[szampino]

Jhm,

I am not a forum expert but I'll give it a whirl.

couple Questions:

1. What kind of pool do you have? How big?
2. What is your filtration method? (Sand/Cartridge)
3. What are you floating? (Trichlor Puck?)


Comments:

Your TA does appear high. I do believe that one of the keys to PH maintenance is TA, so if your TA is high it may mess with your PH.

Your FC is in-line for your CYA.

I have never heard of CYA dropping that much over such a short amount of time. In fact, the only way I know of to lower CYA is to do a partial drain. I'm still a novice on the forum so maybe there is some CYA eating critter out there but that would be the only thing I can think of that would do it.

So given what I know and the information in your post, my first reaction is something is not right with your 'Numbers' post. Are you testing yourself? If you are, What kind of testkit are you using.

[CarlD]

We have some disagreements here-- I've found that with a vinyl pool, personaly, 150 is OK for T/A but others insist 100 is the max. I'm not saying they are wrong, but I haven't had the problems they say can develop...I may have just been lucky.

However, I don't like pH at 7.8 and suggest lowering it to 7.0...then aerate (splashing kids playing are good) to raise the pH back over 7.2. This will lower your T/A as well, killing 2 birds with one stone.

Are you using cal-hypo to chlorinate or shock? That stuff CAN push pH up.

Falling CYA is due to dilution unless you have a NASTY algae bloom.

[jhm]

Hi-

Thanks for the response. I use a Taylor k-2006c kit. I used to use Ben's kits before. I think my numbers are accurate, but I may have missed something.

The CYA is mystery to me too. I had a high CYA a couple years ago, and worked hard to lower it. This year it was really low and I couldn't keep chlorine up. I raised it, but maybe my tests right after I raised it were premature. Or could the conditioner been old?

The TA is a different matter. I don't know how to lower it or if it has a big impact on driving my pH higher. I do know my pH has always pushed higher much faster than I thought it should

Thanks!

[jhm]

Thanks! I have a 25k gunnite pool. I've always shocked with liquid chlorine, never even tried cal-hypo. Our source water my be high in both TA and pH. Maybe I should test that to get a baseline?


However, I don't like pH at 7.8

I don't either, but it's always a struggle keeping it down. I'm dropping it tonight to 7.0 - 7.2 but in a few days I'm sure it will raise back up. It threw me for a loop when Home Depot cut the strength of acid in half without any clue.


Falling CYA is due to dilution unless you have a NASTY algae bloom.

Maybe that's it. I did have to deal with algae when I found my CYA so low (then I raised it to 40) and the sun so hot that chlorine wouldn't last even for a day. Do you think the floater technique will work to keep it in check and raise the CYA?

Thanks!

[CarlD]

Thanks! I have a 25k gunnite pool. I've always shocked with liquid chlorine, never even tried cal-hypo. Our source water my be high in both TA and pH. Maybe I should test that to get a baseline?



I don't either, but it's always a struggle keeping it down. I'm dropping it tonight to 7.0 - 7.2 but in a few days I'm sure it will raise back up. It threw me for a loop when Home Depot cut the strength of acid in half without any clue.



Maybe that's it. I did have to deal with algae when I found my CYA so low (then I raised it to 40) and the sun so hot that chlorine wouldn't last even for a day. Do you think the floater technique will work to keep it in check and raise the CYA?

Thanks!

Checking your fill water is always an excellent idea--ours used to have a t/a of 180.

Lowering T/A is done indirectly. T/A is linked to pH. Not only is it a pH buffer, but as pH rises and falls, T/A rises and falls with it. So....you have to lower the T/A relative to the pH. The way to do this is to lower the pH and bring the T/A down with it.

Then there has to be a way to raise pH without T/A going up again--Borax won't do it, Soda Ash won't do. The trick is aeration.

Aeration sounds fancy but it's not. Leaving your pool uncovered will cause some aeration and pH increase, but lots of splashing kids or a fountain causes it to increase the pH much faster. You can point the return jet at the surface too, that helps. I won't go into the chemistry of the gassing off--in part because I only partially understand it myself.

When pH rises from aeration, you then add acid again to lower it back to 7.0, each time measuring your T/A after you aerate it back up. When the T/A is where you want, it you stop aerating. It's a racheting process.

Since you are having troubles keeping pH down, you could try getting the T/A down to the 80-100 range--100 max--and see if that helps stabilize it. Don't start using Cal-Hypo, but stick with liquid bleach/chlorine...I thought with your CH # you might be since pH was rising to.

If you want to raise your CYA and are fighting rising pH, then Tri-Chlor pucks are an excellent way to do it. Be sure to check CYA every week though and stop using them when you hit your CYA target.

aylad, my fellow mod down in Louisiana, likes to run a much higher CYA than we Northernors, Poconos and myself, do. That's because she faces far more intense sun and heat on a regular basis and it's just easier and cheaper to run the pool with a CYA of 70 or 80 and maintain a residual FC level of 5 to 10 ppm. She actually uses less chlorine that way.

Your K2006-C is really not any different than the older PS-232 and PS-233 kits sold by PoolSolutions--just organized a little differently--and you have the acid and base demand tests as well. It's all Taylor reagents anyway.

Hope this all helps.

[waterbear]

A few things that will help iwth the pH....
First lower your TA to around 70-90 ppm. Once this is accomplished bump your CH up to about 300 ppm. (The reason this needs to be done is complicated so I am not going to give the full explanation here but it's basically because you have a plaster pool).
Second, once your TA is in line keep your pH at 7.6 and not lower. The lower you put the pH the faster it will rise (we use this fact to our advantage when we lower TA). When you pH rises to 7.8 use the acid demand test in the K-2006 to bring it back down to 7.6 and not lower.
Finally, adding borates to 50 ppm to your pool can help with pH stability tremendously. If you decide to add borates there is a very good tutoarial on how to do so here (http://www.troublefreepool.com/so-you-want-to-add-borates-to-your-pool-why-and-how-t4921.html).

[jhm]

Thanks for all the advice. It sounds like I need to work on the TA by lowering pH to around 7.0 for a while. Aeration shouldn't be a problem as we have these things on a couple of returns called Baja Bubblers, giving a fountain type effect. Hmm...maybe those might contribute to my continually rising pH?

Does high pH have any effect on chlorine consumption?

Thanks,

Jim

[szampino]

I kept meaning to ask you if you had some kind of Water Feature in your pool. I used have a fountain and couldn't understand why my PH kept rising. Sounds like you know have a plan.

Good luck.

[CarlD]

Thanks for all the advice. It sounds like I need to work on the TA by lowering pH to around 7.0 for a while. Aeration shouldn't be a problem as we have these things on a couple of returns called Baja Bubblers, giving a fountain type effect. Hmm...maybe those might contribute to my continually rising pH?

Yup. Turn them off for a week and see what happens! Bet pH is far more stable.




Does high pH have any effect on chlorine consumption?

Thanks,

Jim

I don't think it does, (the chem gurus can chime in) but it DOES have an effect on the effectiveness of chlorine...the lower the pH the more effective the chlorine is. But at super-effective levels, your water will be acid enough to melt vinyl (which you don't have).

I tend to prefer pH in the 7.3-7.5 range for just hat reason. Chem_Geek has tables on that --if you dig around you may find them.

[chem geek]

The graphs of chlorine effectiveness vs. pH with and without CYA are in this post (http://www.poolforum.com/pf2/showpost.php?p=32912&postcount=8). The bottom line is that with CYA in the water, it acts to buffer the disinfecting form of chlorine which means the disinfection rate doesn't change that much with pH. Without CYA, going from a pH of 7.5 to 8.0 drops the chlorine effectiveness by around 50% while with CYA it only drops around 15% Of course, without CYA, the chlorine effectiveness is huge so even a drop of 50% isn't a big deal (it's still over a factor of 15 higher at the same FC level when the CYA is 30 ppm).

There is a theoretical increase in the breakdown of chlorine from sunlight at higher pH since hypochlorite ion breaks down about 6 times faster than hypochlorous acid from the UV in sunlight. Though the disinfecting chlorine (hypochlorous acid) doesn't drop much at higher pH, the hypochlorite ion increases a lot to compensate. With an FC of 3.5 and a CYA of 30 ppm, going from a pH of 7.5 to 8.0, the rate of chlorine loss from sunlight is almost tripled. However, we've never done any experiments with real pools to see if this "theory" actually happens in practice. There have been a couple of anecdotal reports indicating that some effect of this sort does occur. Just remember that chlorine loss has multiple sources and we're only talking about the loss due to sunlight in this discussion.

Richard