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Acid Neutralizers
Acid neutralizers that raise the pH of acidic well water before it eats your copper: calcite and calcite/Corosex systems on Clack and Fleck valves, upflow tanks with no drain or power, and the Corosex media to blend or top up. Low pH is the cause behind blue-green stains, pinhole leaks and a metallic taste, and a neutralizer is the fix. Shipped free, built to order, 5-year valve and 10-year tank warranty on backwashing systems. Calcite or Corosex blend? Upflow or backwashing? Sizing and placement are below the products.
Acid neutralizers for low-pH well water
Neutral water is pH 7. Groundwater in much of the Northeast, the Carolinas, the Pacific Northwest and anywhere with granite or sandstone geology comes out of the ground at 5.5 to 6.8, and that slightly acidic water dissolves copper and brass as it passes through the house. The signs are blue-green staining on sinks, tubs and around fixtures, pinhole leaks in copper pipe after 10–15 years, a metallic taste, and elevated copper or lead in a test. An acid neutralizer fixes the cause rather than the symptom: it passes water through a bed of crushed calcium carbonate (calcite), which dissolves slowly into the water and brings the pH up to 7 or above. No chemicals, no dosing, no power on the upflow versions.
Calcite or a calcite/Corosex blend?
| Media | Raises pH from | How it behaves | Use when |
|---|---|---|---|
| Calcite (calcium carbonate) | 6.0–6.9 up to ~7.0–7.5 | Self-limiting: dissolves faster when water is more acidic and stops near neutral, so it can't overshoot. Adds roughly 3–5 grains of hardness. | pH 6.0 or above; the standard choice for most wells. |
| Calcite/Corosex blend (calcite + magnesium oxide) | 5.0–6.0 up to ~7.0 | Corosex is five times more reactive than calcite and will overshoot to pH 8–9 if used alone or in too high a ratio; blended 20–30% with calcite it handles water calcite can't. Adds more hardness. | pH below 6.0, or high flow where contact time is short. |
| Soda ash injection (chemical feed) | Below 5.5 | A Stenner pump doses sodium carbonate; adds no hardness but needs solution mixing and a retention tank. | Very acidic water, or where added hardness is unacceptable. Call us; we build these to order. |
Backwashing or upflow?
Calcite tanks need the bed loosened periodically so it doesn't cement, and on well water with any sediment they need rinsing. A backwashing neutralizer on a Clack or Fleck valve does both automatically to drain; it's the right choice for most wells and the only choice if there's iron or turbidity in the water. An upflow neutralizer has an in/out head and no controls; water rises through the bed and keeps it loose, which works on clean, low-iron water and anywhere there's no drain or outlet. Both need calcite topping up: the media is consumed as it does its job, typically 6–12 months between top-ups, and the tank has a fill port for it.
Sizing a neutralizer
Neutralizers are sized by contact time, which means by flow rate and by how far the pH has to move. The lower the pH, the bigger the bed for a given flow.
| Home | Service flow | pH 6.5–6.9 | pH 6.0–6.5 | pH below 6.0 |
|---|---|---|---|---|
| 1–2 bathrooms | 7–10 GPM | 1.0 cu ft, 10″ × 44″ | 1.5 cu ft, 10″ × 54″ | 1.5 cu ft blend |
| 2–3 bathrooms | 10–12 GPM | 1.5 cu ft, 10″ × 54″ | 2.0 cu ft, 12″ × 48″ | 2.0 cu ft blend |
| 3–4 bathrooms | 12–15 GPM | 2.0 cu ft, 12″ × 48″ | 2.5 cu ft, 13″ × 54″ | 2.5 cu ft blend |
Backwashing units also need the well pump to deliver the backwash flow: about 5 GPM for a 10″ tank, 7 GPM for 12″, 10 GPM for 13″. Send us the pH, hardness, iron and your pump details with a quote request and we'll size it.
Acid neutralizers: Clack and Fleck side by side
| Configuration | Clack | Fleck |
|---|---|---|
| Upflow, no drain or power, calcite or blend, ¾″ or 1″ | Clack Acid Neutralizer (1–2 cu ft; from $649) | — |
| Backwashing, calcite or blend | Backwashing Acid Neutralizer (WS1 valve; from $899) | Fleck 2510 AiQ Calcite Neutralizer (1–2.5 cu ft; from $1,079) |
| Sealed-tank, sized by bathrooms | Pentair Acid Neutralizer (1–3 or 4–6 baths; from $1,299) | |
| Media top-up | Corosex (from $226); calcite by the bag, call to order | |
Where it goes, and what it does to your hardness
The neutralizer is the first treatment stage after sediment and before an iron filter or softener, for two reasons. Iron media and softener resin both need neutral water to work, and low pH shortens their life. And the neutralizer adds hardness as it dissolves (3–5 gpg with calcite, more with a blend), so a softener downstream handles the extra; a softener upstream would be sized wrong. The sequence is sediment, neutralizer, iron/sulfur, softener, carbon, UV. If your pH is already 6.9 and hardness is the only problem, you may not need a neutralizer at all; a softener on slightly acidic water is usually fine.
Frequently asked questions
Does an acid neutralizer make water hard? Yes, by a few grains. It's dissolving calcium carbonate into the water, which is what hardness is. On a well that already has a softener this is invisible; on one without, you may notice slightly more scale. It's the trade for not replacing your plumbing.
How often do I add calcite? Check the level every six months through the fill port and top up when it's down a third; a 1.5 cu ft tank on pH 6.3 water uses roughly half a bag a year. Lower pH and higher use consume it faster.
Can I just use Corosex? Not on its own. Pure Corosex overshoots pH and cements in the tank. It's blended with calcite at 20–30% for water below pH 6.
Will it fix the blue-green stains? It stops new ones. Existing staining is copper that's already come out of the pipe; it cleans off, and once the water is neutral it doesn't return.
Alkalizer or neutralizer? A neutralizer corrects acidic source water to protect plumbing. An alkalizer or remineralizer adds minerals back to water that's been through RO, for taste. The Crystal Quest alkalizing systems on this page are the latter; if your issue is corrosion, you want the calcite units above.
Questions on pH or sizing: call 800-374-2143. Related: well water filtration systems · sediment filters · iron filters · softeners for well water.
