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Operating Swimming Pools at High pH -- How, and Why?

Text © Ben Powell 1998 All rights reserved


If you read this page, and go away thinking that high pH is good, read it again. It's not that simple. Let me repeat: IT'S NOT THAT SIMPLE!! The ideas here are really not for pool beginners.

This page attempts to correct the simplistic pool industry idea that high pH is always BAD, but I don't want to replace that oversimplification with another one.

High pH is NOT always BAD! But, high pH is NOT always GOOD, either!

Introduction to high pH

The recommendation that swimming pools should be operated at pH levels between 7.2 and 7.6 is almost universal. This recommendation is enshrined in generations of pool books and literature. It's embedded in many state swimming pool codes.

Unfortunately, for most swimming pools, it's also far from ideal. While it's quite possible to do a good job with your swimming pool in the standard pH range, it's often harder and more expensive. But, operating at high pH can be tricky or even impossible, if you live in an area such as southern Arizona, where your pool fill water is very high in alkalinity and calcium.

Still, you should know that the recommendations made here are so far from mainstream swimming pool wisdom that they are not even controversial. Instead, most dealers and pool experts would consider them 'totally off the wall'.

Nevertheless, the chemical evidence is clear. I will not make any effort to reproduce it here. Eventually I'll post an article with extensive footnotes, explaining the rationale for high pH pool operation in some detail. But for now, you'll have to take it on faith or pass it by.

So . . . if

  • you are a skeptical (like I usually am), or if
  • you are uncomfortable with the unconventional, or if
  • you simply are unsure . . .
    . . . please just go on back to our sitemap and pick another page!

Simple Chemistry: Complicated Explanations

What this page can't show is how simple the practice of high pH chemistry is. It's extremely easy to use the methods discussed here! In most cases, the instructions for just your pool alone would fit on one side of a 3 x 5 card!

But, every pool is slightly different. And since this paper attempts to address the application of of these methods to most pools, the discussion here has become long and complicated. Further, some of the chemistry itself is both complicated and uncertain. In some cases, I know what usually works, but not why or how.

In other words: following a high pH recipe for your pool is really easy, but knowing how to design that recipe can be really hard.

And now, the not very fine print:

The information on this page is applicable ONLY to pools operating with chlorine or bromine as their sanitizer. You should NOT attempt to use these methods with ANY mineral or copper based alternative sanitizer system, such as

  • Pristine Blue or other copper liquids
  • Caribbean Clear, Carefree Clearwater, or other ionizer systems
  • Nature2
  • skimmer mineral pills of any type
  • zinc based systems
  • or any other system which adds 'minerals' or copper to the water, or which is advertised as "chlorine free", or "chemical free".

And if you use copper algicides, you must use only the recommended dose, and must NOT repeat applications unless the copper level in your water is less than 0.2 ppm. I don't know what would happen with Bacquacil, SoftSwim or the like.

The pH levels recommended here can precipitate copper or silver, which is generally NOT what you want to do. [We do it on purpose sometimes, but that discussion is REALLY complicated!]

If this is making you nervous, please bail out now, and return.


I didn't discover high pH pool operation, and I don't know who did. But I know of a few others who've been recommending or using high pool pH long before I began servicing swimming pools 10 years ago.

PoolClor, a large Western pool service company (30,000+ customer pools), has been operating their customer's pools at high pH (7.8 - 8.2), using borax as a pH buffer since at least the early '60's. In fact, they had what was probably the first California EPA registration for pool use of borax -- long before John Girvan was able to patent algicidal applications of borax to swimming pools.

Jock Hamilton, president of United Chemical, has been recommending high pool pH levels since before I first talked to him, 7 or 8 years ago. (Jock was the first person who gave me a clue toward understanding what was going on in some of my pools -- I'd already stumbled onto some of the benefits, but didn't have a clue as to why they were working so well.)

And, I've been operating commercial pools in my own market for 8 or 9 years at these pH levels.

No doubt many others have stumbled onto at least a portion of the method I'm going to explain here. But it's hard to find this information in print, so here it is. If you get started on this page, and find it confusing, but are still interested, you may want to find out how to get an individualized pool guide.

Why bother?

The simplest answer is the practical one: it's easier and it's cheaper. For some pools, optimized high pH pool chemistry will essentially eliminate mucking around with pH, alkalinity, and calcium. For most pools, it will reduce the work to maintain pH and water balance to them. For a few, it will be impractical or impossible.

In my own work with large commercial pools, we now adjust water balance once, when the pool is filled, and rarely make changes afterwards. We adjust pH monthly: our customers no longer store any acid on site. The total acid consumption at one 300,000 gallon pool has been 50lbs of muriatic acid -- over a 5 year period!

My next door neighbor last summer used a dozen gallons of household bleach, 25 pounds of trichlor, and 4 or 5 boxes of grocery store borax. That was his total chemical consumption (less than $100) for the entire summer with a 14,000 gallon pool. Actually, I haven't checked his garage, but I think he still has some trichlor left.

Pluses and Minuses

Operating your pool at high pH will often, but not always produce these benefits:

  • reduced consumption of sodium bicarbonate (alkalinity)
  • reduced or eliminated consumption of calcium chloride (calcium hardness)
  • reduced or eliminated consumption of acids (pH minus)
  • reduced eye and skin irritation
  • reduced formation of irritating chloramines (combined chlorine)
  • reduced 'chlorine' smell
  • reduced problems following 'shocking' or 'breakpoint chlorination'
  • increase the effectiveness of ammonia based chlorine 'enhancement'.

I suspect (with some evidence) high pH will also

  • reduce halogenated volatile sanitation byproducts (primarily an issue with indoor pools)
  • reduce corrosion of indoor pool enclosures
  • reduce swimmer irritation from high chlorine levels
  • improve control of biofilm forming organisms, e.g. psuedomonas aeruginosa and 'mustard algae'

However, high pH often will also tend to

  • precipitate metals in pool water, such as copper, iron or manganese
  • lower the measured ORP for a given DPD chlorine level (only important if you have and ORP controller on your pool)
  • increase the time required to kill a particular pathogen with a given DPD chlorine level (eg, the Ct value for a given DPD chlorine level)
  • make broadcasting of calcium hypochlorite (HTH) to your pool problematic.
  • increase scaling if your calcium and alkalinity are too high.

Should you or shouldn't you?

If you have a chlorinator on your pool, connected between the pool and the suction side of the pump, or between the pump and the filter, you should not.

If you have a copper level in your pool above 0.2 ppm, you should not.

If you have used copper based materials in your pool this year, and don't know what your copper levels it, you should not.

You have calcium levels above 300 ppm or alkalinity levels above 160 ppm, you should not.

If you don't understand what you have read to this point, you should not!

There are ways around all of the issues (except continued use of copper) above, but they require pool-by-pool application. And in areas where pools have serious problems with scale build up or on pools with pool heaters, extra care is needed. Pools can be run at high pH under those conditions, but setting it up correctly for your pool requires more thought.

If you don't understand what you've read -- and I'm guessing most homeowners and many dealers won't -- you'll need to wait till we offer individual pool recipes. Of course, in some parts of the country, your pool service company may already be using high pH chemistry on your pool!

How do I do it?

In a word, gradually!

Most pools have a 'natural' pH level. What that level is, depends on your sanitizer, bather load, weather and makeup or source water. For many pools, that level will fall between 7.6 - 8.0. When we operate pools, we will allow the pool to drift between 7.4 - 8.2 and only intervene if the pool goes outside of that range, OR if it consistently stays above 8.1 or below 7.6.

This is the most important element of easy pH control: don't fight it, unless you have to!

Some pools, and particularly those using chlorine gas or trichlor, will tend to drift downward, to damaging levels. We've seen pools on chlorine gas reach pH 5.0, and trichlor pools at 6.2! This will cause no end of problems and must be counteracted.

Most of the pool pH problems I get email about fall into three categories:

  • the owner or operator added too much of something (pH minus or plus), or
  • the owner is using trichlor exclusively, or
  • the owner is unnecessarily fighting his pool's 'natural' pH.

It is possible that some pools might tend to drift up above 8.4 by themselves, especially in certain areas of the country. However, in almost every cases, very small amounts of acid will correct this. For every pool problem I've seen solved by adding acid, I've seen ten from adding too much acid! This is a case where more is definitely NOT better than a little.

The second element of easy pH control is: never make large changes in pH!

You should almost always adjust pH very gradually. Use doses smaller than label recommendations. Adjust, wait 24 hours, test, and then only adjust again if you must!

One exception to this rule: if you are using an ammonia containing chlorine 'enhancers', such as ammonium sulfate, aqua ammonia, Yellow Out (tm Coral Seas), or Mustard Buster (tm BioGuard), you MUST get the pH above 8.0 before you begin the process. Otherwise, you'll tend to make a real mess.

The third element of easy pH control is: ignore much of what your dealer tells you about water balance!

Many of our pools will mostly have pH levels close to 7.8, with hardness and alkalinity levels around 100 ppm. We have one pool which stays at 7.7 to 7.9, with alkalinity around 150 and calcium hardness around 240. None of these pools have exhibited either corrosion or scale formation.

The fourth element of easy pH control is: use an inorganic form of chlorine to shock!

Calcium hypochlorite (HTH) is preferred, but sodium hypochlorite (bleach, or liquid chlorine) will work. We can't imagine why anyone would want to use lithium hypochlorite, but it would probably work. Don't use sodium dichloroisocyanurate (dichlor) or trichloroisocyanurate (trichlor) to shock, EVER!

The fifth element of easy pH control is: when lowering your pH, never add acid to your skimmer!

If you need to lower the pH, add SMALL amounts of acid directly to the pool. If you use sodium bisulfate (dry acid), predissolve it (CAREFULLY, while wearing eye protection) and add it to the pool. Muriatic acid is cheaper and better for your pool (once diluted), but more dangerous and harder to handle.

The sixth element of easy pH control is: when raising your pH, add borax through the skimmer!

Don't use soda ash. You can get borax at the grocery store (green box, 20 Mule team brand). The correct amount? Add a cup at a time on small pools, and 2 cups on large pools, wait 24 hrs, and check your pH. Add more if you need to. Make SURE your skimmer basket is in place.

The seventh element of easy pH control is: add chemicals to raise alkalinity and calcium to 100 - 120, only after the pH is 7.6 or higher.

Never adjust these while your pH is below 7.6. Always add these chemicals through the skimmers, never broadcast into the pool. (Make SURE your skimmer basket is in place.) Adjust your calcium first, then your alkalinity. Don't try to change them both at the same time. Once you get them adjusted, don't fight them, if they stay in the ranges above. (As I've noted elsewhere, it is usually NOT necessary to add calcium to a vinyl pool.) ---

The eighth element of easy pH control is: shock, and adjust alkalinity and calcium before, not after, backwashing.

We've discovered a method of shocking that produces greatly improved results in many cases. In conjunction with high pH pool operation, it can make management of alkalinity and calcium levels easier, especially if your pool levels run high. BUT, depending on the type of equipment you have on your pool, it can also damage pool equipment, or even be dangerous. So, we usually only explain this on the forum (PoolForum.com) in the middle of careful discussions of how and how-not to do this.

The final element of easy pH control is: listen to your own pool!

Ask virtually anyone who's been servicing pools for more than a year or so, and they will quickly tell you every pool is different. Swimmer load, shade, overhanging plants, pump & filter combinations, etc. -- all pools respond differently. We tell new customers we will do a really good job with their pool the first year, but an even better job the second, when we've gotten to know the pool. You can do the same thing: you know what your pool should look like, feel like, yes, even smell like when things are going well. When things aren't right, many times you can tell just by looking at your pool.


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