Trouble keeping pH in proper range after switch to SWCG

Jump to latest Follow Reply
C

CraigMW

0
LifeTime Supporter
May 19, 2011
697
Orange County, CA
Recently, I installed an IC60 SWCG along with an Easytouch 8 for our in ground white plaster pool. The system has done a very good job of generating chlorine, but I just can't seem to keep the pH in range. It seems to go up very quickly, to the point where I'm having to add over 2ga of 14.5% HCl every week and still not achieving appropriate pH. I think I'm also starting to see evidence of greyish discoloration and scaling in the pool. These are the numbers I got tonight using the TF100 kit:

FC 6.5 (FAS/DPD)
CC 0.0
pH 8.2 (from what I can tell)
CH 620
TA 180
CYA 80
Borates 0
TDS?
SALT 3200 ppm

I know that both my TA and CH are too high, but I really don't want to do a water change unless completely necessary. The water was changed out about 3 years ago when we bought the house and had an acid wash then.

From what I've read, Borates might help to buffer the pH. I'd really like to keep the pH in the range of 7.4 to 7.8. Do I really need to drain a bunch of water and start again with lower CH and TA levels to help reduce scaling and pH buffering? Should I dial back the amount of chlorination via the IC60? I've been running it at 40% for about 8hrs/day and the chlorine range seems high, but okay for the CYA level. Before the SWCG, I rarely had to add acid to keep the pH range around 7.5 or so, but ever since, it has been a problem as described.
 
Having high TA and a SWG will make the pH continually rise.

If your water is clear, start working on lowering the TA following the article in Pool School. Once in range you can then consider borates to also help stabilize the pH.

With the high CH it is important to get the pH and TA under control.

Posted from my Droid with Tapatalk ... sorry if my response is short ;)
 
With CH above 500, you will want to keep your PH range max level closer to 7.6. Is this a newer plaster pool? The SWG and your water features, coupled with high TA is causing the PH rise. In a 38k gal pool, 2 gals of MA is not all that much and you'll need plenty more to reduce TA to a more managebale level. What is the CH and TA of your fill water?
 
You don't need to drain any water to get you ph/ta levels manageable. It's an easy fix... it will take a little patience, but not difficult.

With your TA that high and an swg your ph will continue to swing upward as it acts like aeration in the water. The best way to solve it is to get yourself some muriatic acid and every time your ph moves up... say to 7.8, bring it back down to 7.2 and aerate your pool. Turning your return jet upward to create bubbles on the surface is what I have done before to make the process happen faster, or you can just lower it gradually as you notice your ph has drifted up. Lowering your ph with m.acid will bring down your TA, when your ph climbs again, your TA will remain lower. Continue the process until you reach the desired TA level of 60-80 for an swg pool. With the amount of CH you have, you may want to aerate if you can to make the process go faster so you don't have problems with calcium scaling.

You don't want to use borates to help stabilize your ph until you have reached a ph that is manageable for your pool already.
 
Thanks to all who have replied! It's great to hear I can do this without draining the water, esp. since So. California is perpetually in a drought. We also have water that is very high in calcium, e.g. it is very hard water. I haven't measured it yet, but I would imagine that just to start, it is probably over 300. Regarding the question about how old the pool is, I really don't know. Based on the age of the equipment, I would imagine that the last plaster job was probably done about 8-10 years ago. Actually, the plaster looks very good if that age is true... only a few subtle grey splotches if you look carefully. But, I'd like to get a couple more years before having to replaster, so with such high CH, I need to make sure to not have a pH overshoot again. Once I get this in balance, I may invest in a feeder system like the IntellipH or IntelliChem.

I added two gallons of 14.5% muriatic acid from HD last night and now my water is in the 7.5 pH range, which is pretty much right on with what the pool calculator comes up with. This also dropped the TA from 170 to about 150. I will definitely need to add plenty of acid to get this down even further. I guess I need to find a stronger source of MA so I don't have to drag as much liquid around.

As for aeration, we have a rock waterfall that results in a huge level of aeration, so I can program that to run for several hours a day to help increase the pH. It all seems so counterintuitive though. Why would the SWCG lead to an increasing pH? It would seem that the hydrolysis taking place in the SWCG would lead to more acidic water, right?
 
Another factor that I had not considered before that may also be contributing to this... Our pool has an attached spa and I've always had at least a little bit of return water routed to the spa to maintain proper chlorine levels in the spa. When I set up the Easytouch about a month ago, I adjusted the return valve actuator so that it would stop at about 75% of its travel. This probably means that the spa is getting 30-50% of the return flow directed towards it. This of course then empties into the pool via a small overflow ledge (maybe 6-8 inches above the pool water level). The flow has been quite a bit more pronounced since I did this. Maybe I need to cut the water flow to the spa so that it's only getting maybe like 10% of the return flow?

BTW, any difference between using muriatic acid vs. some of the solid acid powders out there? Also, is it possible to chelate the high calcium and then vacuum it out? After testing our fill water, I've found that it is at 350 ppm, so I'm already starting at a high reference. My former pool guy used to keep our pool dosed with cal-hypo tablets in a floating dispenser, and I'm sure that must be how the pool achieved such a high CH number.
 
I don't know if there is any way to remove the calcium, someone else will have to answer that one.

As far as the acid you use, muriatic is probably the lease expensive way to go. What they carry in pool stores to decrease ph may be easier to lug home, but more expensive. I don't know that there are any other acids safe for pool use.

Cal-hypo in combination with your already high calcium fill water certainly didn't help your CH level at all. Try and get your TA into range and then keep your ph in balance and hopefully then you will be free of any problems. Your Ch level is really high, so you'll want to still be on the watch for any scaling problems.

Anything that causes bubbles to break the surface can cause your ph to rise... so a spillover spa, water feature, swg all are able to force you ph up. Even once you get your TA in check and your ph balanced, you'll want to routinely monitor your ph closely with all the aeration your water gets.
 

Enjoying this content?

Support TFP with a donation.

Give Support
I know 14.5% is popular in Cali, but perhaps you can still find 31.45% at your local paint store or masonry supply shop. That's alot of acid lugging especially with a fairly large pool, spilover/waterfall and SWG...all aeration sources.
 
The smaller pool stores do 31.45% in refillable bottles - it'll be the kinda place a smaller pool service company get's it's supplies.

Have you tested the TA of the fill water? Adding as much acid as you have been should be reducing your TA somewhat already. If the TA of your fill water is high that will counteract your efforts to lower it - so you'll need to be aggressive in your attempts to raise PH to crush that TA number.
 
You must log in or register to reply here.
Thread Status
Hello , This thread has been inactive for over 60 days. New postings here are unlikely to be seen or responded to by other members. For better visibility, consider Starting A New Thread.
Top Bottom
Back
Jump to latest Follow Reply