How to Fix Acidic Well Water: Raise the pH With a Calcite Neutralizer (What to Buy, Where It Goes)

People ask me, "I have acid water, what do I do to treat it?" Usually they have just gotten a water test back and the pH is low, say 5.5, and the sink has a blue-green tint it never used to have. This page is the answer I give on the phone: how to know the water is really acidic, what it is doing to the house, the one piece of equipment that fixes it, which size to buy and what goes in it, where it goes in the line, and what changes once it is in.

How to tell your well water is acidic

Water below pH 7.0 is acidic; the EPA's guideline range for drinking water is 6.5 to 8.5, and the number I want to see after treatment is 7. As I told a caller in Georgia whose test came back at 6.0: on the pH scale you want to get to seven, and that eliminates corrosion. Below 6.5 the EPA itself lists the effects as a bitter metallic taste and corrosion.

The signs show up in the house before anyone tests the water. Blue-green stains in a white sink or tub, a copper or metallic taste, pinhole leaks in copper pipe, and water heaters that die young are the four I hear most. One buyer in a house he had owned two years wrote that a stainless steel pump was corroding, the copper he cut out while re-plumbing was strangely thin, and the dog would only drink from a plastic bowl; his pH turned out to be a full point low. If you are seeing any of that, the signs of acidic water page walks through each one, and blue-green stains has its own page because it is the one people search for most.

A test settles it. Of the 339 certified lab reports from the well water test kits people buy through us, 8 percent came back below pH 6.5 and 17 percent below 7.0, and the acidic ones were nearly all soft water. Soft and acidic go together. A Maryland caller was surprised his hardness came back at zero; that is exactly why his water was so acidic. There was no soft rock for it to dissolve on its way through the aquifer.

So test for more than pH. When a customer texts me a report, I look at the pH, the iron, the hardness, and anything else that came back high, because those three numbers decide the tank size, what goes in it, and whether you need any other equipment. If you have older plumbing or staining, also test copper and lead at the tap; Virginia Tech's guide recommends the same. A hardware store strip kit is fine for a first look (a New Hampshire caller's home kit "matched up pretty well" to the $150 lab test he had already paid for), but the lab test is what gives you iron, hardness and copper in one report.

What acidic water does to a house

Low pH is not itself the health problem; the problem is the copper and lead that acidic water dissolves out of your own plumbing on the way to the tap. The EPA's action level for copper is 1.3 ppm, and it lists the effects as stomach distress in the short term and liver or kidney damage over the long term; for lead the action level is 0.015 ppm. Both metals get into the water when the plumbing corrodes, and low pH is what causes that corrosion.

Our own lab data shows the link: below pH 7, about one test in six had copper over the EPA action level; at 7 and above, about one in a hundred. Same kits, same lab, same kind of houses.

The other cost is the plumbing itself. Pinhole leaks are copper being eaten from the inside, and a water heater on acidic water wears out early; both have their own pages (pinhole leaks in copper pipes, acidic water and your water heater). Once the pH is corrected the corrosion stops, and a verified buyer who had lab copper at an unhealthy level on pH 6 water wrote that after the neutralizer took it to about 7.4, a retest showed copper well below the threshold for concern. Metal that has already been eaten out of a pipe does not grow back, so I would rather you fix this at pH 6.4 than wait for the first leak.

Why well water turns acidic in the first place

Rainwater is acidic, and it stays acidic unless it passes through rock that can neutralize it, which is why a well in limestone country comes up hard and a well in granite or sandstone comes up acidic and soft. Here is how I explain it on the phone: all water that seeps into the ground is acidic because it is rainwater. As it passes through iron-bearing rock or soft rock like limestone, it breaks that rock down and carries it into the water. So you get hard water, or iron in the water, or both. Where there is nothing soft to dissolve, the water arrives at your pressure tank still acidic and still soft.

Two things come out of that. First, your neighbor's test tells you very little; I have been into neighborhoods where twenty houses sat on twenty different aquifers with twenty different analyses. Second, a well can change: a different aquifer can come into the one your well draws from and change the chemistry completely, so the test from when you bought the house is not permanent.

The fix: a calcite acid neutralizer

An acid neutralizer is a tank filled with crushed limestone; the water flows through it, dissolves a small amount of the calcite, and comes out neutral. It is what a limestone aquifer does underground, done in a tank in your basement. Calcite is calcium carbonate. Nothing is injected, and the non-backwashing models do not even plug in. As the calcite dissolves the tank slowly empties and you refill it; that is the only maintenance, and it is covered below under Keeping it working.

The reason I trust the design is that it regulates itself. The tank can only raise the pH so far, and where it tops out depends on the mix you put in; with the standard mix it settles between 7 and 8 and stays there no matter how much water you use. The non-backwashing tanks we sell are plumbed so the water enters at the bottom and flows up through the whole bed of calcite (this is called upflow). A plate at the bottom spins the water so it cannot cut a channel through the bed and skip the calcite. We have been using them for twenty years.

The other way to raise pH is a chemical feed pump that injects soda ash or caustic soda ahead of the pressure tank. We do not recommend it and we do not sell it. University extension guides list it as the option for water below about 5.3, and the same guides say it is more complex and needs significant regular maintenance. The people who call me with one are usually calling because it is not doing the job: a Maryland homeowner starting around pH 4 had a caustic soda injector and had already given up on calcite ("the rocks", as he put it) because it would not bring his pH up. That is because it was not mixed with FloMag. We treat wells in the threes with a 2.5 cubic foot tank and a calcite-and-FloMag mix fairly easily. If you want the full comparison, it is on acid neutralizer vs chemical feed system.

Under two minutes on camera: the two ways to treat low pH and why we only sell one, where the tank goes, what changes the first week, and what the maintenance actually is.

Here is what it actually does to the pH. Nine of our verified buyers wrote both their before and after pH into their reviews; every well that started at 5.5 or above finished between 7.0 and 8.0. The one that did not reach 7 started at 4.8 on a 2.0 cubic foot tank; that case is explained under What goes wrong.

Which neutralizer to buy

Three numbers choose the tank: your pH decides what goes in it (plain calcite, or calcite plus FloMag), your iron decides the type (non-backwashing or backwashing), and pH plus household size decides the tank size. The table is the same one I run through on the phone. Prices are what the tanks sell for on our site today and include the calcite and shipping; every one is also on the acid neutralizer collection page.

Your water	Photo	What to buy	Price today	Why
pH 6.0 to 6.9, iron under 0.5 ppm, 1 to 2 people		1.5 cu ft non-backwashing, plain calcite	$1,295	Small household, mild acidity
pH 5.5 to 6.9, iron under 0.5 ppm, 3 or more people (or anyone at pH 5.5 to 6.0)		2.5 cu ft non-backwashing, plain calcite	$1,495	The tank most callers end up with: more calcite, fewer refills
pH below 5.5, iron under 0.5 ppm		2.5 cu ft non-backwashing, calcite + FloMag	$1,695	Below 5.5 the calcite needs FloMag mixed in
Iron 0.5 ppm or more, any pH below 6.0		2.5 cu ft backwashing (Fleck 2510SXT), calcite or calcite + FloMag	$2,195 / $2,395	Iron needs a tank that flushes itself (read the next section first)
Crawl space or closet under 48 inches		1.0 cu ft non-backwashing, plain calcite	$1,195	Fits under 48 inches; refills more often

Why the iron row is different: a non-backwashing tank has no way to flush out trapped iron, so at 0.5 ppm of iron or more the backwashing Fleck 2510SXT, which rinses itself through a 1/2 inch drain line, is the right tank. With iron and a pH of 6.0 or above you may not need a neutralizer at all; that is the next section. The 1.0 cubic foot is the same tank in a shorter body for crawl spaces and low ceilings.

Two notes on the mix. The standard mix is 2 to 3 pounds of FloMag per 50 lb bag of calcite, stirred together in a bin before it goes in the tank; the FloMag option on the product page adds the FloMag to your order. The ratio can go higher. A New Hampshire caller with a pH of 3.27 got 6 pounds per bag, because on the Eastern Shore of Maryland we treat pH levels down in the threes all the time. University extension guides say a neutralizer only works down to about 5.3; with a custom mix, the lowest well we have taken on was 3.67. If you are below 5, text me the report before you order and I will give you the ratio. How the two media differ is on calcite vs Corosex, and mixing is on using FloMag.

On size: when a caller is deciding between the 2.0 and the 2.5, I tell them to go with the 2.5. It gives you better flow rates and more capacity, and you will service it a lot less. The full sizing table by household size is on the sizing guide; what the whole thing costs over ten years is on acid neutralizer cost; if you want to see the models compared head to head, that is the best acid neutralizer page; and everything about these systems in one place is the Complete Acid Neutralizer Guide.

Ask Aidan

Have the test in hand and not sure which row you are in?

Text me the pH, iron and hardness, or a photo of the report. I'll tell you which tank, what to put in it, and whether you need anything else.

Text Aidan 443-277-2204 Call800-460-5810Aidan

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Where it goes, and what to do if you also have iron

The neutralizer goes after the pressure tank, with a sediment filter ahead of it, and before anything that removes iron or hardness. That is the order in the video and the order on our equipment order guide. Low pH gets corrected first because, as I told the Maryland caller at pH 4, when it is that low you need to get it up before the water goes through anything else. The sediment filter traps dirt before it reaches the calcite.

Iron is the big fork in the road, and the old version of this page skipped it. A neutralizer does not touch iron. A New Jersey contractor building his own house had read that a neutralizer "usually lowers the iron level," and I had to tell him no: raising the pH takes care of the acidity, and that is all the neutralizer does. Iron stays in the water and stains the bowl. So when a test shows both, the plan depends on how low the pH is:

The New Hampshire caller at 3.27 ended up with all three tanks. The reason is the iron filter: it needs water near pH 8 to remove iron properly, so the neutralizer has to bring the water up to 7 first. If your iron is the bigger problem, the neutralizer and softener page and the iron filter pages cover the other two tanks.

Installing it: we recommend a licensed plumber for the install, but get familiar with the equipment so you can handle routine service too. Verified buyers describe the job as a couple of hours; one connected to existing copper with 18-inch flexible SharkBite lines onto the recommended CPVC fittings, another with 3/4 inch PEX and brass. A backwashing model also needs a drain line, and 1/2 inch is the size. The walkthrough is on how to install an acid neutralizer, and watch the videos first: one reviewer noted that several install tips in the videos are not in the written instructions.

What changes after it goes in

Within the first week the blue-green stains stop, the copper taste is gone, and the plumbing and appliances stop corroding; the water also comes out three to six grains harder than it went in. One verified buyer had pH at neutral within 24 hours. The hardness is the part to plan for. Calcite is calcium, and dissolving it into the water is what raises the pH, so the water gets harder. Acidic wells are usually soft to begin with, which is why most people never notice; a buyer at 6 to 6.5 who finished at 7.5 to 7.8 wrote that his water was still in the soft range.

What I tell customers is to put the neutralizer in, let it run for a week or two, then retest. If hardness is below 7 grains you are good to go and do not need a softener. At 7 grains and above, appliance manufacturers recommend a softener, and it goes after the neutralizer. Retest copper and lead at the same time if they were elevated before; the pH fix stops new metal coming off the pipe, and the retest is how you know the number at the tap has actually come down.

Certified lab test, $199

Retest two weeks after the install

One certified lab test, mailed to you, run by an accredited lab, shows your new pH and hardness, plus copper and lead at the tap. If all you have right now is a strip reading, the same test gives you the numbers you need before you buy.

Get the certified well water test

53 contaminants. Results reviewed by Aidan, in plain English.

If the pH ends up above 7, that is normal. One reviewer went from 6.2 to 7.99 and worried it was too much; the tank regulates itself, tops out where the mix puts it, and 7 to 8 is where we want it (an iron filter deliberately runs the water to 8 or 8.5). The slippery, soap-will-not-rinse feel people associate with high pH does not show up until the pH is around 9 or 10.

Keeping it working

Look in the tank once a year, and add a 50 lb bag of calcite when the level has dropped, which on a 2.5 cubic foot tank at pH 5.5 with four people is about every 24 to 36 months. That is the only recurring job (the bag is heavy to lift, as one reviewer pointed out, and that is the hardest part). Smaller tanks and lower pH need refilling sooner: about 6 to 12 months on the 1.0 cubic foot, 18 to 24 on the 1.5, 24 to 30 on the 2.0, and 30 to 36 on the 2.5 in typical water. A calcite-and-FloMag mix is topped off on the same schedule, because the FloMag is only a few pounds of each bag.

A non-backwashing tank needs nothing else. A backwashing tank flushes itself on the schedule set at the valve, using the same 1/2 inch drain line the old one used if you are replacing a system. The step-by-step, including how to drain and open the tank, is on servicing your acid neutralizer, and the bags are in the shop: calcite, 50 lb and FloMag, 50 lb.

What goes wrong

When a neutralizer is not working, it is usually one of five things: the wrong mix for the pH, a tank too small for the house, expecting it to do something it does not do, a backwashing tank whose calcite has hardened, or a skipped hardness retest.

• Plain calcite on very acidic water. The 4.8 well in the chart above finished at 6.5 on a 2.0 cubic foot tank. That points to the mix, not the tank: below about 5.5 the calcite needs FloMag in it, and at 4.8 I would want to see the report before setting the ratio. The fix is usually FloMag mixed into the next refill, not a second tank.
• Undersizing. A tank that is too small for the household does not give the water enough time in contact with the calcite, so the pH creeps back down under heavy use. This is why I steer callers to the 2.5 for a family house even when the pH alone would allow a 2.0.
• Expecting it to remove iron. It will not, and it never did. If the bowl still stains after the pH is fixed, the iron was there all along and needs its own filter or a softener (see the iron table above).
• A backwashing tank whose calcite has hardened into a block. The New Hampshire caller's eleven-year-old backwashing neutralizer had, in its own manufacturer's words, turned to concrete. Channeling means the water cuts a path through the calcite and skips most of it. In a backwashing tank it starts at the top, and the backwash does not have the power to lift and turn the bed, so the channel stays until someone opens the tank and stirs the calcite with an old broomstick or a length of pipe. The upflow design of the non-backwashing tank avoids that on wells that do not have iron.
• Skipping the hardness retest. A house at 6 grains before the neutralizer can be at 10 or 11 after; the two-week retest above is how you catch it.

If the pH is still low with the tank in, check how much calcite is left first; a low tank means less calcite for the water to touch. If the tank is full and the pH is still low, the mix needs FloMag or the tank is too small. Text me the pH going in and coming out and I can usually tell you which over the phone.

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