pH Water Filter: How to Fix Low pH Well Water (Complete Guide)

Caller "Our pH is like four and a half to five. Is that pH system just like a dosing pump?"

Aidan "No, these are neutralizer tanks. The tank is thirteen by fifty-four. It stands right next to the pressure tank."

That was a caller in April, and it is the question behind most of these calls. People hear "pH filter" and picture a pump or a cartridge, and Google shows them pitchers. What fixes acidic well water is a tank of crushed limestone, and that is the thing in the photo.

What a pH water filter is

A pH water filter for a well is a tank of calcite that the water passes through on its way into the house, and the calcite raises the pH to about 7. Water comes from your well acidic, say 5.5. It passes through the tank, comes in contact with the calcite and slowly dissolves it, and that raises the pH to a neutral level. The industry calls it an acid neutralizer. Customers call it a pH filter, a pH neutralizer, a calcite filter, or "that pH system." Same tank.

The caller in the opening had it half right. There is a version of pH correction that uses a pump: a soda ash injection system, which meters a chemical solution into the line. We do not use them. Most customers do not like the fact that they have to maintain it on a monthly basis. A neutralizer tank has no pump, no electricity and no drain in the non-backwashing form, and the only upkeep is adding calcite every 18 to 36 months. It stands right next to the pressure tank, and a plumber connects the inlet and outlet to the main line. The tank in the photo above is 13 inches wide and 54 inches tall.

The rest of what the tank does is in the video below, which is the guide I made on these systems. If you would rather read, the how an acid neutralizer works page goes through the chemistry and the self-regulating part in detail.

Which "pH filter" fixes well water

Only a whole-house tank treats the water before it reaches your pipes; a pitcher or an under-sink cartridge changes one glass or one faucet and leaves the plumbing on acidic water. When you search "pH filter" you get four different things with the same name. Here is what each one is and what it does for a house on a well.

Photo	What Google calls a pH filter	What it treats	Fixes low pH well water?
	Alkaline water pitcher or bottle	One pitcher of drinking water. Adds minerals so the glass tastes alkaline.	No. Every pipe, the water heater and every other tap stay on acidic water.
	Under-sink cartridge that adds minerals back	One faucet. Adds minerals back to drinking water after a reverse osmosis unit strips them out.	No. Same problem as the pitcher, one tap at a time.
	Whole-house calcite tank (crushed limestone), sold as an acid neutralizer	Every drop entering the house. Raises the pH to about 7 before the first pipe.	Yes. This is the pH filter for a well. Plain calcite handles pH down to 5.5. Below that I add FloMag, a stronger mineral.
	Chemical feed pump (soda ash injection)	Every drop entering the house. A pump feeds a chemical solution into the water line.	Yes, but it is a pump you mix for and maintain monthly, not a filter. We do not sell them.

The mix-up is common enough that I hear it from people who already own equipment. A caller in April had a company install whole-house reverse osmosis and "a little canister alkaline filter" after it, and his pH was still reading 6.5 to 6.8. A canister on one line is not going to change what the copper pipes see. Another caller on city water asked me about the remineralizing stage on an RO unit, and I told him what I think: it is more of a gimmick than anything else. The tank does one plain job on all the water.

Ask Aidan

Not sure which row you are looking at?

Text me a photo of what you found, or the product page, and your pH if you have it. I will tell you whether it treats the house or one tap.

Text Aidan443-277-2204 Call800-460-5810Aidan

8 AM to 5 PM Eastern, seven days a week. A real person, usually Aidan.

Is the limestone tank natural?

Yes. Calcite is natural limestone, nothing chemical goes into the tank, and the water stops dissolving it once the pH reaches neutral. A caller in July put it to me straight: "You just put this calcite in there, which is limestone, right?" Right. It is self-regulating: once the water gets to a neutral pH, it stops dissolving the calcite. It is a very effective and very efficient way to raise the pH without using chemicals. The reason well water runs acidic in the first place is a lack of minerals in it. The neutralizer adds calcium back, which is the opposite of adding a chemical.

One honest limit. If your pH is below 5.5, plain calcite in a 2.5 cubic foot tank will not hold 7 by itself, so I mix in FloMag, which is magnesium oxide, a couple of pounds to each bag of calcite, more when the pH is very low. It is a mined mineral too, but it is stronger, and too much of it can push the pH past where you want it. The FloMag page covers the ratios. The only non-natural way to raise pH for a whole house is the soda ash pump in the table above, and the soda ash versus neutralizer page is the fair comparison.

Does your pH need one?

Anything below 7 is acidic, and the further you go below 7, the more aggressive the water is on your plumbing. You cannot see or smell acid water, so the best thing to do is get a basic test from Lowe's or Home Depot, or send a sample to a lab, and find out what your pH is. The hardware-store kits only read down to about 5, so if the strip pegs at the bottom, the real number could be lower. The lab test gives you the number to a decimal, and it also reports the copper the acidic water has already pulled out of your pipes.

Of the wells my customers have had lab-tested, about one in six came back under 7. The copper number is the one that should move you: about one acidic tap in six had more copper than the EPA allows (10 of 64), against about one in a hundred at pH 7 and above. The EPA lists corrosion of household plumbing as where that copper comes from. If you already have blue-green stains in the tub or a pinhole leak, the signs of acidic water page shows what each one looks like.

Already have a lab report? Skip this. No number yet: certified lab test, $199

One sample tells you pH plus copper

One certified lab test, mailed to you, run by an accredited lab, gives you the pH that decides whether you need the tank, the hardness that tells you what comes after it, and the copper already at your tap.

Get the certified well water test

53 contaminants. Results reviewed by Aidan, in plain English. On city water, use the city water test.

Where the tank goes

The neutralizer goes after your well pressure tank and sediment filter, and before an iron filter or a water softener. People ordering several pieces of equipment ask me which goes first. After your well tank and your sediment filter, the neutralizer goes first, then the iron filter, then the water softener.

For a new well that tests acidic and soft, the typical setup is a sediment filter after the well tank, then the 2.5 cubic foot neutralizer with plain calcite, and a softener after that only if you want soft water. The installation page has the connections, and I recommend a licensed plumber does the work; I support your plumber by phone at 800-460-5810.

What changes after the tank goes in

The pH comes up to about 7 and the water gets a little harder, about 4 to 6 grains. The first couple of weeks can also read high while the calcite dust settles. The hardness comes from the calcium the water carries out of the tank, and it is real. Plenty of buyers live with it; one whose water was only slightly acidic wrote that they "did not bother with a water softener." The appliance makers recommend a softener once the water is at 7 and above and carrying hardness. If you want soft water, a softener goes after the neutralizer, and the acid neutralizer and water softener page is where I answer whether you need both.

The other thing to expect is the start-up. A caller in June who had just installed his "black 2.5 pH filter" with FloMag got a reading over 8.5 and worried. Just let it run. When you first start them up there is a lot of dust in the calcite, the water can run milky, and the reading jumps; it can take a couple of weeks to settle down. It always jumps up at first. Back when we still installed them ourselves, it happened all the time. Test again after two weeks, with a strip or a meter, before you decide anything.

How much it costs by size

The pH picks the tank size, not the bathroom count. I recommend the 2.5 cubic foot non-backwashing tank to most callers because it holds 7 on plain calcite down to 5.5 and needs a bag the least often. Each of these has its own page, so I will keep it to one line each.

• Size. The pH sets the size. Plain calcite holds 7 down to about 6.0 in a 1.5 and down to 5.5 in a 2.5; below that, FloMag goes in. A 10x54 tank needs calcite every 6 to 12 months where the 2.5 goes about every 36. The sizing guide works it through.
• Cost. Non-backwashing with plain calcite: 1.0 cubic foot $1,195, 1.5 $1,295, 2.0 $1,395, 2.5 $1,495, shipped with the calcite in bags. Add $200 for the FloMag blend. The Fleck backwashing 2.5 is $2,195. A 50 lb bag of calcite is $145. The cost page has the yearly numbers.
• Type. Non-backwashing (upflow) 99% of the time. I only go to a backwashing tank when iron is 0.5 parts per million or higher. They both raise pH the same way; backwashing has nothing to do with pH levels, whatever someone may tell you. The backwashing versus non-backwashing page has the rest.
• Install. What ships: the tank, the valve with the bypass pre-installed, the fill funnel, and the calcite in separate 50 lb bags, loaded at install. A licensed plumber typically completes the install in 2 to 3 hours; the install page shows the connections.
• Service. Check the calcite level once a year with a flashlight against the translucent tank and keep it about 10 to 12 inches below the fill port. On a 2.5 that works out to a bag every 18 to 36 months. The servicing page has the steps with photos.

What buyers said

Verified buyers of these tanks, with the pH numbers they reported. Each of these is a verified purchase through our store; reviewer names appear as the buyers wrote them.

Frequently asked questions