Water heater sediment: signs, causes and how to remove it

What sediment is and where it comes from

A. O. Smith says tap water contains minerals that form sediment in the bottom of the tank and lime deposits on electric heating elements, and that the amount depends on the hardness of your water.

Not all of it is minerals. Bradford White describes the tank as acting like a filter for the house: over thousands of gallons, whatever particles come in with the water settle there. It says many cases of so-called rusty water turn out to be sand and clay sediment, from private wells or from water main breaks that let mud into the system.

Signs your tank has a sediment problem

If the bits are white or translucent and look like plastic, they may be a breaking dip tube rather than minerals (see water heater dip tube). Brown or rusty water has its own causes (see rusty brown hot water).

Why it matters

• Efficiency. A. O. Smith says sediment or lime build-up can reduce the efficiency of the heater. Bradford White quotes the Air-Conditioning, Heating and Refrigeration Institute (AHRI) saying sediment can reduce energy efficiency and also clog water lines.
• Damage. A. O. Smith says heavy deposits can damage the water heater, and that draining sediment extends the life of the tank, elements and drain valves.
• Burned-out elements. Bradford White's service manual says sediment or lime around an element can eventually create an air pocket and dry-fire it within seconds (see bad electric element).
• Noise. A. O. Smith ties popping and rumbling to sediment on the tank bottom (see why is my water heater making noise).

How to remove it

Drain and flush. This is the standard fix. A. O. Smith's steps: turn off the gas or power, run a hot faucet until the water is cool, connect a hose to the drain valve, shut the cold supply, open the drain valve and a hot faucet. If a lot of sediment comes out, open the cold supply with the drain still open and let water run through until no more sediment drains. Our full walkthrough is in how to flush a water heater.

If it won't drain. A. O. Smith says sediment can form large masses that keep the tank from draining, and that a qualified person can use a de-liming agent suitable for drinking water to remove them.

Electric elements. In very hard water, A. O. Smith says to remove and check the elements whenever you drain the tank, and that it's usually easier and cheaper to replace lime-encrusted elements than to clean off heavy deposits.

Tankless units don't collect sediment the same way but do scale up inside; they're descaled with a pump and solution instead (see how to flush a tankless water heater).

How often to flush

A. O. Smith recommends draining and flushing after the first six months of operation to see how much sediment builds up. If there's little, flush once a year; if there's a lot, flush more often. Bradford White passes on AHRI's suggestion to flush the tank each time you check the relief valve. The Department of Energy's Energy Saver Guide suggests draining a quart of water from the tank every three months to remove sediment.

Hard water makes it worse

The harder the water, the faster sediment builds. Some of the towns we serve have very hard water. Xenia, Ohio's water report says the city doesn't soften its water and calls it very hard, at close to 400 mg/L (23 grains per gallon). Canton also calls its well water very hard. A. O. Smith's advice to flush more often with hard water applies here.

A water softener reduces scale, but A. O. Smith notes the anode rod will deplete faster with softened water, so inspect it more often (see water softeners and water heaters).

Is sediment harmful?

The sediment in a tank is mostly what was already in your water, concentrated in one place. The bigger concern is usually for the heater. If you want to know what's in your water, your utility's annual Consumer Confidence Report lists what it tests for and finds; the EPA explains how to find yours. On a private well, test the water directly.

Local pages mentioned

• Xenia, OH
• Canton, OH