Acid Neutralizers: The Complete Guide to Fixing Low pH Well Water

If your well water's pH is below 7.0, it's acidic and slowly corroding your plumbing, appliances, and fixtures. An acid neutralizer is a tank filled with natural calcite (limestone) that raises the pH as water flows through it. The non-backwashing kind needs no chemicals, no electricity and no drain.

You can't see or smell acidic water, so a test is the only way to know you have it. Anything below 7 is acidic, and the lower you go away from 7, the more acidic and the more aggressive the water is. This guide covers the whole job in order: what low pH means, the two kinds of tank, what goes inside them, the size and the price, what ships and how it goes in, and how to keep it working. Each part links to the full guide for that question.

What Is an Acid Neutralizer?

An acid neutralizer (also called a pH neutralizer, calcite filter, or pH water filter) is a whole-house water treatment system that raises the pH of your water from acidic to neutral. It's a tall tank filled with natural calcite media (calcium carbonate, essentially crushed limestone) that slowly dissolves into your water as it flows through, raising the pH.

It goes on the main line after your pressure tank, so every faucet, fixture and appliance in the house gets neutral water. Raising the pH to neutral is what stops the corrosion of your plumbing and your water-using appliances. The how the tank works guide goes through it part by part, and the video below is the whole topic in five and a half minutes.

You will also see it sold as an acid neutralizer system, an acid neutralizer filter, an acid water neutralizer, a water neutralizer system, a pH neutralizer for well water, an acid neutralizing filter, an acid neutralization tank, a whole house water neutralizer or a calcite tank. They are all the same tank of calcite on the main line, so when you compare quotes, compare the tank size, the valve and what goes inside, not the name.

What Low pH Means

Water with a pH below 7.0 is acidic, and the further below 7 it is, the more aggressive it is on metal pipes. The EPA's recommended range for drinking water is pH 6.5 to 8.5, and it lists low pH as a cause of corrosion and a bitter metallic taste. That range is one of the EPA's secondary standards, which it describes as guidelines for taste, color and odor rather than health limits.

The bigger question is what acidic water picks up from your pipes. Copper is the one you see: the EPA's secondary standard for copper is 1.0 mg/L, for its metallic taste and blue-green staining. The 1.3 mg/L number you may have read about is different. That is the action level under the Lead and Copper Rule: when more than 10% of the customer taps a public water system samples are above 1.3 mg/L, the system has to take extra steps to control corrosion. Whether your own water is safe to drink depends on your test, and the is acidic water safe to drink guide covers that question.

A hardware-store pH strip tells you quickly whether the water is acidic today. To size a neutralizer, I want a lab number for pH, and the same sample tested for iron and hardness, because each one changes what you buy.

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One certified lab test, mailed to you, run by an accredited lab, reports pH, copper, iron and hardness from the same sample, which are the numbers this guide keys off.

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Signs Your Well Water Is Acidic

The signs show up in your copper, because acidic water dissolves it on the way to your faucets. A blue-green stain in the tub, the shower or the toilets you use most is dissolved copper.

• Blue-green stains. The blue-green stains guide shows what they look like and what else can cause them.
• Pinhole leaks. Little pinhole leaks in copper pipe, which can open inside a wall and cause a lot of water damage before you find them. See pinhole leaks in copper pipes.
• A metallic taste. Copper and low pH both taste bitter and metallic. Iron can too, which is why the metallic taste guide sorts out which one you have.

You can't see or smell the acid itself, so the test above is how you confirm it. The signs of acidic water guide has every sign with photos.

How Does an Acid Neutralizer Work?

Acidic water dissolves a little of the calcite as it passes through the tank, and the dissolved calcite is what raises the pH. Calcite is calcium carbonate, so the calcium it leaves in the water is also why a neutralizer adds a little hardness.

In a non-backwashing (upflow) tank, the water comes in at the valve, goes down the center tube, comes out through the slotted plate at the bottom and rises up through the calcite to the outlet. There is no motor and nothing to plug in. In a backwashing (downflow) tank the water flows down through the calcite instead, and an electric valve on top reverses the flow on a timer to rinse the bed to a drain.

The tank is self-regulating: the less acidic the water gets, the more slowly it dissolves the calcite. That is why plain calcite is far less likely than a FloMag blend to push your water too high; the highest plain-calcite reading in our verified reviews is 7.99. The point of filling the tank is to make a wall of calcite the water has to pass through; when a caller told me he had put one bag in his 2.5, I told him, "One bag in that tank wouldn't do anything."

Non-Backwashing vs. Backwashing

For most homes the non-backwashing (upflow) tank is the one to buy; the backwashing kind is for water that also has iron above 0.5 ppm or heavy sediment. Both raise the pH the same way. Backwashing has nothing to do with pH levels, like some people might lead you to believe; it only keeps iron and sediment from fouling the calcite. 99% of the time, I use the upflow tank.

A backwashing tank ships set to backwash every 3 days. With no iron in the water I set it to every 7 days; with iron, every 2 to 3. Orders for the Fleck 2510 tanks now ship with the 2510 AiQ valve, Pentair's replacement for the discontinued 2510SXT. The backwashing vs. non-backwashing guide has the whole comparison, and the tanks themselves are under non-backwashing (upflow) neutralizers and backwashing neutralizers.

What Goes Inside the Tank

Plain calcite alone works down to pH 5.5 in the bigger tanks (2.0 and 2.5) and down to 6.0 in the smaller ones (1.0 and 1.5). Below those numbers, FloMag, a magnesium mineral that dissolves faster than calcite, is mixed in.

Calcite is crushed limestone, granular and a little bigger than sand. FloMag is never used by itself: it is mixed into each box of calcite in a bucket or bin before it goes into the tank, and never measured as a percentage. A caller at pH 5.6 asked me whether he needed it, and I told him, "You're above five point five, so you'd probably get away with just plain calcite." The calcite vs. Corosex guide compares the two, and how to mix FloMag shows the bucket method. Calcite is $145 a box and FloMag is $225 a bag.

How to Size an Acid Neutralizer

Your pH decides the size first, and the number of people in the house decides it second. The majority of the time I recommend the 2.5, because it is one size that fits most houses: plain calcite handles pH down to 5.5 in it, and it goes the longest between top-offs. When in doubt, bigger is better.

On a non-backwashing tank, your well pump's gallons per minute has nothing to do with which size you buy. More than 8 people, a pH below 5.0 or a spot you are not sure about: send me the numbers first. The acid neutralizer sizing guide goes through every case.

Know your pH and household size?

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Send your pH, how many people live there, whether you have iron and the height of the spot. I'll tell you which size, whether it needs FloMag and where it goes in your line.

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What an Acid Neutralizer Costs

The acid neutralizer systems in the table below cost $1,195 to $2,395 shipped, depending on the size, the type and whether it gets FloMag. Every price below includes free shipping to the lower 48 states, and the calcite it ships with.

On top of the tank there is the plumber and the calcite. Putting in a non-backwashing tank is usually about two hours of a plumber's time, and around $800 is a fair benchmark for a straightforward install; local rates, access and any repiping your basement needs can move the quote either way. After that, calcite runs about $50 to $145 a year on a 1.5, 2.0 or 2.5 tank, and $145 to $290 on a 1.0, at $145 a box. A full re-bed every 5 to 10 years takes the same number of boxes the tank ships with in the table above: $290 on a 1.0, $435 on a 1.5, $580 on a 2.0, $725 on a 2.5 and $1,015 on a 3.5, plus FloMag at your rate if your water needs it, from the bag you kept or a new one at $225. If your water is hard as well as acidic, the neutralizer + softener packages pair the two from $3,095. The tank carries a 10-year warranty and the valve 5 years, against manufacturer's defects. The acid neutralizer cost guide adds up the purchase, the plumber and ten years of top-offs.

Installing an Acid Neutralizer

I recommend having a plumber put it in, and I'm a phone call away for your plumber. If you'd rather do it yourself, text me with any questions.

A non-backwashing tank is the smallest kind of job: there is no drain line and no electricity, just an inlet and an outlet, so it is about 2 hours of a plumber's time. A backwashing tank adds a 1/2 inch drain line with an air gap to a floor drain, standpipe or utility sink, and an outlet for the valve; that drain line is the part that takes planning, and the job runs about 2 to 3 hours and about $800.

What ships:

• The empty Vortech tank and the control valve, with the bypass valve included
• The calcite in separate 50 lb boxes, all of which goes into the tank at install, and on the FloMag version a bag of FloMag, mixed in at the rate for your pH with the rest kept for refills
• The fill funnel for loading the calcite

What does not ship: the pipe and fittings, which your plumber brings for your kind of plumbing (the valve has 1 inch connections), and on a backwashing tank the drain tubing. There are no instructions in the box either; the manufacturers figure a plumber is putting it in. Systems ship in 3 to 5 business days.

Your plumber cuts into the main line after the pressure tank, connects the inlet and outlet to the bypass valve, and loads the calcite through the funnel. Any copper between the well tank and the neutralizer should be cut out and replaced, because the water in it is still acidic. The step-by-step installation guide and its video are the instructions I give plumbers.

Where the Neutralizer Goes in Your System

The neutralizer goes on the main line after the pressure tank and a sediment filter, and before a water softener. If you have more than one problem, the order is what makes each piece work.

If your water has iron too, send me the test and I set the order from it. Iron above 0.5 ppm also means the neutralizer should be a backwashing one. The acid neutralizer with a softener guide covers the two-tank setup for water that is both acidic and hard, and the complete guide to well water filtration systems covers the full treatment order when a well has more than one problem.

What to Expect After Installation

Plain calcite usually brings the water to about pH 7.0 to 7.5, depending on where your water starts. A FloMag blend can push it higher, to about 8 or 8.5. The first readings after a fresh fill can run high from the fine dust in the calcite, so give it a couple of weeks before you judge the number.

Across the 32 homes in our verified reviews that give both numbers, the median went from pH 5.5 to 7.3, and 26 landed between 7.0 and 8.5. Five stopped between 6.5 and 7. The one reading over 8.5 was 10+, from a 2.5 filled three quarters full with a 10% FloMag mix, about twice the rate the table above gives for his starting pH of 5.4; after he vacuumed the media down to half full, it settled in the high 8s.

When the tank first fills, the water at the faucet comes out milky white from that same dust. Run a cold faucet until it is clear, which takes about 5 to 10 minutes.

The calcite adds about 3 to 6 grains per gallon of hardness. Test again after the neutralizer: if the water comes out at 7 grains or more, add a softener after it. The buyers quoted further down describe the pH they got and whether the water pressure changed.

Maintenance and Servicing

Check the calcite level once a year and add calcite when it is about halfway down. The tank is semi-translucent: turn the room lights off, hold a flashlight against the back of the tank and look from the front. The water above the calcite glows, the calcite stays dark, and the line between them is your level.

Very acidic water and heavy use shorten those intervals; a weekend house stretches them. Fill to about 10 inches below the fill port. The new calcite goes on top of the bed that is there; there is no need to empty the tank first. To refill, shut the water off to the tank, open a cold faucet to relieve the pressure, take out about a 5 gallon bucket of water, take the fill port cap off, set the funnel in and pour or scoop the calcite in. Then cap it and refill slowly with a cold faucet open until the milky water runs clear. The refill guide has every step with photos. The 5 micron cartridge in the sediment filter ahead of the tank gets changed about every 4 to 6 months on a typical well.

Topping off is the routine, but it is not the whole job forever. Even with a sediment filter, a little very fine sediment gets past it and builds up in the bottom of the tank, so every 5 to 10 years, closer to five on a well with a lot of sediment, the tank should come off the line to be emptied, rinsed out, sanitized and refilled with new calcite, plus FloMag at your rate if your water needs it; the refill guide covers that clean-out too. If the water pressure drops before then and the neutralizer looks like the cause, have the bed checked: sediment built up in it can mean it needs the same clean-out sooner.

Acid Neutralizer vs. Chemical Feed System

A chemical feed system is a pump on a 15 to 30 gallon solution tank that injects soda ash into the water line every time the well runs, and done right, a retention tank after it (usually 80 to 120 gallons) so the soda ash can blend in. You mix the soda ash with water in the solution tank about once a month. A calcite neutralizer is one tank, with no pump and no chemicals to mix. I do not sell soda ash feed systems.

Soda ash does have real advantages: it adds no hardness, where calcite adds about 3 to 6 grains; there is no bed of calcite for the water to push through; and the dose can be turned up or down at the pump. A feed pump makes sense when you cannot add any hardness and will not run a softener, or you want to set the dose yourself, and someone will keep up the monthly mixing, test the pH now and then and look after the pump. The neutralizer vs. chemical feed guide compares the two side by side, and soda ash vs. an acid neutralizer covers switching off a soda ash system you already have.

What Buyers Wrote After Installing One

These are verified purchases, listed by date and quoted as written. The rest are on our reviews page.

A Detailed Guide for Each Question

Each question below has its own guide that goes deeper than this page.

Frequently Asked Questions