Constantly High PH

by Ian Sim
(Palmdale, Ca)

I have a pool of approx 25,000 gallons that was re-plastered in late Nov 2011. Outside temp was in the 50 day time and mid 30's at night. It took 40 hours to refill the pool with water. In coming water PH is 7.2.

After filling and start up completed by pool company, I had a really hard time keeping the PH below 8.2. I added pH Down by the pounds. The PH would drop to 7.4 / 7.6 for a day of so then back up.

I called Plaster company back in Jan as I had granular build up that felt like sandpaper when rubbed. They said that this is what happens when you don't treat a pool for 6 to nine months. They where dumbfounded when I told them that they had just re-plastered two months ago.

They decided that the only way to get rid of the build up to to acid wash my two month old re-plastered pool. They acid washed the pool heavily to remove and completed start up themselves.

Since that date, early Feb 2012 I retained a pool maintenance company to document the pools treatment. They are out every Wed and check pool water and I also check it every week-end also.

Since the acid wash to date ( 4 month )the pool has used 16 gallons of Muratic acid to hold the pools pH level between 7.6 and 8.2. The pool company adds 1/4 to 1/2 gallon on wed and I have to add another 1/2 Gallon usually on Sundays to knock the PH back down. The numbers.

Chlorine good at 2 to 3
TA 80
CYA 50
Calcium Hardness 225
TDS 575

Phosphates started at 100 Feb 2012, now up to 250.
pH today before adding 1/2 gallon of Muratic acid 8.2 with pool equipment running for min of 3 hours after adding, pH down to 7.8

Plaster company says they have no idea, but it can't be from the plaster job. Four different pool maintenance companies also have no idea what is causing the high pH. They all say it must be the plaster.

Help, don't know what to do.

Thanks for the question Ian and sorry to hear about your issue

This is an area of debate and one huge area that has alot of chemical equations. Your issue is the re-plastering and pool start-up.

For years the pool industry has used 3 kinds of start-ups for pools. They are:

- Acid start-up. Keep the pH at 4.5 and alkalinity at zero for three days

- pH neutral. 1 gallon of acid was added to an 8000 gallon pool and balanced out after 3 days

- Traditional. The pool water has a slightly increased alkaline condition for 3 - 4 days, then balanced.

Then came along a new, and I think better, way to balance the pool and help the plaster. It's called the "Bicarb" start-up.

The acid start-up is the worst and most detrimental method. The pH of muriatic acid is already 4.5 so you can see what it can do to a newly plasterd pool.

This kind of start-up does help the surface look good for a while, but it will deteriorate and stain easier.

Without going into too much detail and repeating what I've learned about the bicarb method, you can go to this link to learn much more:

To fix the pH issue, you need to know which kind of start-up the pool company used.

In effect, the bicarb start-up method adds enough bicarb to the fill water before adding it to the pool so that the alkalinity and calcium hardness equals 500.

Bicarb startup essentially adds enough bicarbonate to the fill water before adding it to the pool so that the TA + CH is equal to 500.

The fill water now has a pH level of 8.3 but will increase when the water is added to the pool because of the curing of the plaster. It can be lowered using muriatic acid to around 7.6 - 7.8.

The first month your total alkalinity (TA) remains high and the pH is kept slightly below 8.2.

There's a calcium carbonate surface on the newly plastered surface. By keeping a neutral or slightly positive Saturation Index (SI), you'll prevent the calcium carbonate in the surface layer from dissolving.

Normal range for this is -0.5 to +0.5. The Saturation Index is how well the pool is balanced with the chemicals added. 0.0 is neutral. But even if you keep the SI positive, the pH will still increase.

What's happening now in your pool is the plaster is converting from calcium hydroxide into calcium carbonate. It's like layers of an onion. First layer is calcium carbonate and the 2nd is calcium hydroxide.

Here's something that you might be interested in. To my understanding the calcium carbonate forms on the surface. The underlying plaster areas remain calcium hydroxide as such because it's too deep for the water to penetrate, react, and convert the plaster into calcium carbonate.

But, if the newly formed calcium carbonate is somehow dissolved, as in the case of an acid wash, then it will expose the underlying calcium hydroxide layer, The hydroxide will be released, which will cause the pH to rise.

Like I said early on, this is a huge area with lots of chemical equations.

Take a look at the link above. That has so much information that it would be difficult to write about.

Find out the kind of start-up the pool company used and you can go from there. In my opinion, doing an acid wash on a newly plastered pool is wrong. It's like rubbing sand paper on a new born baby. The skin is delicate so don't do it.

My opinion is the start-up may not have been done properly, but again, without knowing the kind of start-up that was done, it's hard to say.

To post a reply, or if you have a similar question, you can see your post on the Q&A page in the "Start Up/Opening A Pool" category.

Check back to this post for updates or answers.

If you need immediate assistance (within 24 hrs) or for emergency personal assistance, you can make a donation of your choice and I'll answer your questions by phone.

Contact Me


Hope this helps and have a great Summer.


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Jul 09, 2015
How do I keep the ph level from rising in the pool
by: Wayne

I work on a pool at a campground with an indoor pool. The capacity is approx 45000 gallons. Up until this year I have never had a ph problem was always about 7.6. This year for some reason the ph will not stay stable. I have to add about 1 gallon of acid every 7 to 10 days. The owner is very frustrated and thinks it is my testing. I use a taylor drop type kit for testing. The alkalinity of the pool is about 140 to 150. The computer test at the pool store does not usually match my readings.

I think I am very careful with the readings and use 5 drops of phenol red to test ph.There is a small leak in the pool as it is older and I replace about 150 to 200 gallons of water per day. Pool repair is not an option in this case.(owner) I am about ready to throw in the towel and tell him to get someone else to do the pool work. Any help would be appeciated.

Thanks for the question Wayne. We can talk about some of the reasons why pH can go up and troubleshoot from there. First is splashing around. This releases CO2 from the water and causes the pH to rise. That's a Law of Physics/Chemistry so you really can't do too much with that. Next is the use or over-use of sodium bicarb (baking soda/TA Up) and/or sodium carbonate (pH Up). Then there's the fill water, either from a well or city. If you're trying to keep the pH at 7.4 - 7.6 but the fill water is 8.2 it will slowly increase. If you're losing about 200 gallons per day that would equate to about 7% loss of water from 45k gallons. The TA range is 80 - 120ppm. Try to get that down as low as you can and the pH may stabilize.

And last would be using calcium hypochlorite for weekly chlorination and super chlorination. Cal hypo has a pH of 12. If you're using any kind of granular chlorine I'd advise you to immediately stop and switch to liquid chlorine.

Check these out and see if any apply to your situation, or perhaps a combination of them.

If you feel your situation is more complex than this, I do phone and/or SKYPE consultations. It makes things go much faster and many people have found it extremely beneficial, saving them time and money in the long run. All your questions will be answered. I have nothing to sell you so you know I'm not bias. If you purchase a personal phone consult you'll get all 3 eBooks for free.

Pool Consultation

Clear Blue Pool eBook

How To Clear Up A Green Pool eBook

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Hope this helps and have a great Summer.


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