Easy Pool Chemistry

Disinfection Oxidation
Algicides pH
Alkalinity Calcium
Stabilizer Metals
TDS Temperature

This page was originally written in 1997 and hasn't been significantly revised. Since that time, there have been two major changes. First, salt water swimming pool chlorination has become the dominant new method of sanitizing your pool. With salt pools, it's usually easier to operate at a slightly lower pH than what we've recommended. More significantly, with the help of many PoolForum users, and particularly "Chem_Geek", we've worked out how to operate a pools successfully at much higher stabilizer levels than those shown here. The overall approach I developed and published here, and promoted on the PoolForum since 2000 has become known as the BBB Method (for Bleach, Borax, & Baking Soda).

But, if your stabilizer is in the ranges shown here, then the info here is still basically correct.


Be lazy the smart way: do only what your pool needs and no more. But, always do what it needs.

Do what's critical, first: if your chlorine levels is between 2 and 10 ppm, and your pH is between 7.2 and 8.0, it's not likely anything else will get worse. Once you've controlled these two key elements, you can relax a bit about the other things. (Of course, if your stabilizer is LOW and if it's sunny, you won't be able to maintain chlorine levels.)

Don't fight your pool: work with it. Most pools have a pH level they 'want' to be at. For many pools, this will be in the 7. 6 - 8.2 range. Adjust everything else (except chlorine levels) around your pH, and you will reduce your work load tremendously.

Remember, your goal is water quality, not a number. If your pool looks good, is odorless and comfortable, scale doesn't form, and your water is crystal clear -- that's what you are aiming for. It's possible for a pool to be like this, and be unsanitary (have disease causing organisms present), but unlikely. And the plan we're giving will make that REAL unlikely!


Your pool is UNIQUE: learn its rules! Pool chemistry would be easier, if all pools were alike. They are not. Every pool will operate differently, even compared to a nearly identical pool just down the street. Some things are universal: low pH (below 6.8) will damage ALL liners. Some are not: not all pools have a 'natural' pH level that is acceptable. Learn to operate YOUR pool!

Don't believe the anti-chlorine hype generated by folk who want to sell you something. MOST of the problems with chlorine are actually results of using it improperly. Chlorine is NOT perfect, but most of the anti-chlorine info comes from folks who want to sell you something else. Usually, the solution is not to abandon chlorine, but to use it properly.

The rules are the rules, except when they're not! Almost everybody likes simple when it comes to pool chemistry. But, sometimes, simple is not an option. For all sorts of reasons, there's hardly a recommendation on this pool that I haven't broken on purpose, for one reason or another. I try, when I'm discussing an exception, to explain why, but I don't always remember to do so.

Fixing things the wrong way, will often make them worse. Pool miracle chemicals aren't. If your filter and pump have problems, you can compensate a bit, with higher chlorine, but you can't fix those problems chemically. If your pool is foamy because you added crummy algaecides, or if you are getting stains, because you put a bunch of copper algaecide in the pool . . . using a defoamer or a stain/scale chemical, won't really help and can make things worse.

Disinfection and Sanitation

Maintain an adequate sanitizing residual of a primary sanitizer - chlorine:

Sanitizer minimum maximum test
Chlorine 0.3 ppm 15.0 ppm* 3x week

If you want to enjoy a clean and safe pool this is by FAR the most important factor!

All chlorine compounds increase chlorine. But they vary in what else they add to the pool water. For example, 'dichlor' (sodium dichoroisocyanurate) adds stabilizer and not much else but HTH (tm) (calcium hypochlorite) adds alkalinity, calcium AND raises the pH somewhat.

One more thing. Acceptable chlorine levels vary with other factors. When your pool is cool, your pH and stabilizer low, so should be your chlorine. Higher water temperatures, higher pH and stabilizer levels all call for -- or allow -- higher chlorine levels.

Avoid letting your chlorine level actually reach zero, even briefly. If you do, you can recover, but you will experience a noticable deterioration in water quality for up to 3 days. And, you may grow algae!

* IMPORTANT: Unless you have a drop count chlorine test (each drop = 0.5 ppm of chlorine), you can NOT go this high. Convention kits will not allow you to distinguish 7 ppm, which is fine, from 30 ppm, which is WAY too high!


Maintain an appropriate pH:

pH minimum maximum test
All 7.6 8.2* 1x week

If a good chlorine level is the most important factor for you, a good pH level is the most important factor for your pool. Low pH can damage or destroy most pools!

 [ Update: with salt chlorination pools, it's usually easier to operate at a slightly lower pH than what we've recommended here. The "don't fight your pool" dictum still applies. Don't go below 7.0 however, simply because you'll loose control if you do.

A pool's pH level affects many things. The chlorine levels shown will reduce problems with chloramines, reduce eye irritation, and dramatically reduce the work required to maintain pH, alkalinity and calcium levels. Neither I, nor anyone I've spoken to, has ever seen plaster corrosion at these levels -- regardless of alkalinity and calcium.

Use small doses of sodium bisulfate (or muriatic acid, if you know how to use it safely) to lower pH, and small doses of borax (grocery store) to raise pH.

* Do NOT maintain your pH at a higher level than you can test for: if your kit only goes to 8.0, that's your maximum! Also, some pools require constant additions of borax to stay above 7.4.

And, an EXCEPTION: if you have problems with staining, metals in your fill water (well water?) or scale, you may not be able to keep your pH this high, without problems. But, do NOT let it stay below 7.0 for any length of time!


Shock periodically with a hypochlorite: bleach or calcium hypochlorite:

Oxidizer minimum maximum test
Chlorine 3.0 ppm 10.0 ppm n/a

If you maintain the pH and stabilizer levels recommended, you do NOT have to wait for chlorine levels to drop. Of course, it is desirable to shock after you finish using the pool in the evening. And, your swimsuit will last longer if you wear the old one, or the none one, when chlorine is above 5.0.

Shock no earlier than 2 hours before sunset. And make sure the pump will run for at least 1 hour after you shock. Do NOT use dichlor, trichlor or lithium hypochlorite to shock. If you have metals in your pool or tap water, special measures may be needed to protect your pool from staining when you shock.

The best method of shocking cannot be used on all pools: it depends on your equipment layout. As a result, we cannot include it except in a PoolScription.


Avoid routine use of algicides, but when you use them, use enough:

Algicide minimum maximum test
polyquat 1.0 ppm 8.0 ppm n/a
bromide* 2.0 ppm 8.0 ppm n/a
monochloramine* 2.0 ppm 10.0 ppm n/a
copper* 0.2 ppm 0.4 ppm n/a

Polyquat can be used freely, but it's really more effective at preventing, then at curing. A 8.0 ppm dose in a clean pool just before vacation is a GREAT idea.

The other algicides require pool specific instructions to use correctly. Try to avoid using them. Do NOT use the foamy discount algaecides sold in gallon jugs!

The algae in your pool is partially resistant to whatever sanitizer you use regularly. (Environmental adaptation at work!) Consequently, temporary doses of another algicide, with which your own personal strain of algae are not acquainted, can help. But regular use of any product promotes development of resistant organisms.

The copper levels above are typical of many ionizer system standards, and also of some copper algicide products. Overdosing with copper is far more likely to cause long lasting problems than overdosing with chlorine (which is called 'shocking', and is generally recommended!). I have personally seen pools and hair stained green with copper algicides, and pools stained black and gray with copper from ionizers.

* Use these products ONLY as a last resort!


Maintain an appropriate total alkalinity:

alkalinity minimum maximum test
All 60 ppm 130 ppm 1x month

Raise alkalinity with small doses of sodium bicarbonate (baking soda).

Many people -- including dealers -- get alkalinity and basicity mixed up. A base raises the pH level of water and raises the alkalinity as well. But alkalinity is not simply how basic (or high) the pH is. Rather, alkalinity is a measure of how hard it is to change the pH.

An easy way to imagine it is like this: picture a seesaw. If one end is down, the seesaw is 'acid'. If the other end is down, the pH is 'basic' (or, sometimes 'alkaline'). If the seesaw is easy to move, the seesaw is low in alkalinity. If the seesaw is hard to move, it is high in alkalinity.

Actually, there's a bit more to it than that, but unless you are a chemistry buff, you don't have to get into that bit. The main thing is to have some alkalinity, so your pH won't wander all over the place.


Maintain an appropriate calcium hardness level:

calcium minimum maximum test
All 70 ppm* 1000 ppm 1x month

*There's no need to worry about a minimum calcium level in a vinyl or fiberglass pools: the purpose of the calcium is to protect the swimming pool plaster or Marcite.

Never add calcium hardness if your level is 120 or above. Pool specific control measures may be needed in high hardness areas.

Too much calcium and you'll get calcium deposits (usually white or light gray) on the tile at the water line and in your heater, if you have one. You can also end up with cloudy water, though this is not the most common cause of cloudy water.

Calcium is VERY important if have a Marcite or plaster pool and mostly use trichlor for sanitation. Trichlor is acid and will tend to push the pH too low, if you don't watch it. Low pH + low alkalinity + low calcium = high costs replastering your pool!

Adding calcium is easy; getting rid of it is hard. The standard method is to drain and refill. You can also use RO (reverse osmosis) or nanofiltration -- these methods work if you gotta do it and gotta lotta bucks. There's an easy cheap way that works sometimes, but it is pool specific, and may not work on all pools.

Stabilizer (cyanuric acid)

Maintain an appropriate stabilizer level:

Stabilizer minimum maximum test
Chlorine 40 ppm 150 ppm 1x month

Stabilizer is not optional on outdoor pools: the active form of chlorine is quickly destroyed by sunlight. While stabilizer reduces the activity the chlorine present, without it, you will tend to have no chlorine in your pool. Under full sun with clear water in a shallow pool, your chlorine level can go from 5 ppm to 0.1 in three hours! Weak, stabilized chlorine is MUCH better than no chlorine.

However, the more stabilizer in the water, the less active the chlorine you have is. It's not lost or wasted, though. When sun, or goop, consumes the 'active' chlorine, the stabilized chlorine compounds 'release' some of the chlorine, replacing what you just lost. However, if your stabilizer level is higher, your normal chlorine range will need to be adjusted upward to compensate.

And, you don't need to stabilize indoor pools: there's no sun inside (well, hardly any). Actually, there may be a reason to use small amounts of stabilizer on some indoor pools, but I'm still testing this. If you are having operational problems on an heavily loaded indoor pool -- residential or commercial -- and are ALREADY following the other recommendations on this page, contact me.

Metals minimum maximum test
All 0 ppm 0 ppm* 1x month

* may be up to 0.5 ppm during algicidal application. However, copper algicides are a last choice for multiple reasons.

The rule about metals is this: if you didn't put them there, they shouldn't be there. Iron (Fe) and copper (Cu) are the usual suspects, when it comes time to point fingers at stains, which come in green, blue, greenish blue, yellow, brown and orange flavors. Manganese (Mn) is fairly uncommon, which is fortunate because it can make a real mess of your pool.

Most dealers seem not to remember to ask homeowners to bring in tap water samples. Troublesome metals in the pool often arrive in the tap water. Well water is very frequently contaminated with metals. Since pools are much more sensitive to metal contaminated water then is your stomach, water that's fine for you may make a mess of your pool. And just because the water analysis at your local treatment plant shows no metals, doesn't mean that you have no metals. A common source of iron and copper contamination are aging water mains.

Although metals can be a problem for all pool owners, those with plaster pools need to be careful: plaster is more easily stained than are painted, fiberglass or vinyl pools.

Temperature minimum maximum test
All 78 94 as needed

Pool temperature is a difficult and contentious issue. Unlike air temperatures, one degree water temperature changes are IMMEDIATELY detectible by most users. The human body is exquisitely sensitive to relative temperature differences, and in water a one degree shift is enormous.

If you are building an indoor pool, use other pools at different temps to find out what you want, and than build for that. Also, remember that as you age, you'll want warmer water.

The bozo promoting the 78 - 82 'ideal' temperature ought to be placed for 30 minutes in a locked dark room with fifteen 70-year-old arthritis class participants after someone readjusts 'their' pool from 88 down to 86.

The best rule I can offer, is this: in hot sun, some people enjoy water temps down to 70, but not for long. Indoors, almost everyone is miserable below 78, and most folk are unhappy below 84. Above 90 is too hot for almost everyone, except older people with mobility and joint problems. And . . . no matter how cold an 9-year-old is, they will stay in the water till they are hypothermic, if they are having fun!


Don't worry about it. If every thing else is OK, it's not significant.


Notes about Temperature:

The whole topic of comfort engineering pools is enormously complicated and apparently poorly understood even by practicing design engineers, judging by all the mis-sized HVAC and dehumidification equipment I've seen.

Multiple factors come into play, including the fact that "sensible" heat is NOT the determinant of a wet pool user's comfort level while in the air space! Swimmer and pool user comfort is affected greatly by activity level, personal body fat, body mass to surface ratios, activity and metabolic levels, expectations, mobility, net radiative heat exchange, and multiple other factors. Anyone who tells you that there is a particular 'ideal' pool temp for multiple types of pool users is merely demonstrating their own ignorance.

The problem is compounded in commercial environments by control strategies currently embedded in the most sophisticated dehumidification systems that implement some of these conceptual errors.

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