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Water Heaters 101 > Sediment

What you'll find on this page: The single thing that most water heater owners have in common is that they know they're supposed to "drain their tanks" to extend their lives. That's in the water heater instructions and it's because of sediment buildup. But that advice falls short, for reasons you'll understand as you read this page on what causes sediment, what it does to water heaters, and the possibilities for effectively getting rid of it.

A pile of sediment from the bottom of a water heater

"I had to replace my water heater last year. When I drained the old tank, a lot of sand came out."

Our friend had a close encounter with sediment. It wasn't sand in his water heater, although the two sometimes bear a close resemblance. It was calcium carbonate, a mineral present in water which the heat causes to precipitate out, and which settles into the tank bottom, where it does all kinds of bad things.

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High on the list is forming a layer of insulation between the gas burner and the water. The sediment slows heat transfer and overheats the tank bottom. Overheating weakens the steel and damages the glass lining, hastening the day when the tank will fail altogether. In the case of electrics, it can bury the lower element, causing it to burn out.

It also creates a playground for corrosive anaerobic bacteria and lowers the energy efficiency of the tank. Sediment can drift into recirculation lines, jam open check valves, and cause the recirc pump to stick until it burns out.

It can also clog your drain valve, keeping you from getting any water out of it in a disaster, when the heater may have the only clean water supply left.

Finally, it causes noise, sometimes enough noise to annoy, or even frighten people if the tank is inside a dwelling. The noise is caused by small amounts of water under the sediment layer turning to steam bubbles, which then collapse violently.

Water softeners are one solution to mineral sediment buildup, but if you use them, be sure and keep a close eye on the sacrificial anode, as softeners can consume those rapidly, and then the heater is likely to rust out.

Water heater design often doesn't lend itself to controlling sediment. The cold-water inlet, called a dip tube, is straight on many water heaters made today. That means the water strikes the bottom of the tank and causes the sediment to settle evenly on it instead of making it gravitate toward the drain.

Most manufacturers boast "self-flushing" dip tubes that supposedly keep the water so stirred up that sediment doesn't have a chance to settle. We have our doubts about these, especially when low-flow fixtures are used, and we prefer to actually eject sediment from a water heater.


Also the flue that runs down the center of gas-fired tanks creates an additional obstacle to sediment removal. Most tanks, both gas and electric, have domed bottoms so that sediment falls out toward the edges and stays there.

Standard drains are minuscule plastic affairs that can easily be clogged by one large flake of sediment.

However, a brand new tank can easily be prefitted before it's installed. That involves removing the drain valve and installing a brass 3/4-inch ball valve and hose adapter. The ball-valve has a straight-through path that makes it harder to clog and easier to clear if it does clog. The straight dip tube can be pulled out and a combination curved dip tube and nipple installed. The curve makes the water swirl the sediment around the flue and toward the drain. A tank so fitted can be flushed by simply hooking up a hose twice a year and letting the water run for 4-5 minutes under pressure.

If you want to learn how to do this, check out our Know-How page.

Tanks can also be retrofitted, but it's more complicated. A tank that's been in service six to seven years can present problems. If galvanized nipples were used, those can rust on the inside and break off. The plastic drain valve may have become brittle with heat and time and snap off. That doesn't have to be a catastrophe, but it can be quite disconcerting to find yourself staring at a broken valve while 40 gallons of hot water are glug, glug, glugging out.

If you buy these parts from us, we'll provide instructions, of course, but another possibility is to hire a plumber to do it. Interestingly, some who have done this have been told by the plumber that it can't be done. If that happens, contact us.

There are also chemical applications for removing sediment. Some are dangerous, all are time-consuming. The safest is Mag Erad, a citrus-based solvent.

But using these flush parts regularly will ensure that sediment, bits of rust -- and with aluminum anodes -- loads of jelly-like aluminum corrosion byproduct don't build up on the tank bottom, something that's not only bad for the heater, but bad for you if you had to drink them!

If disaster strikes and water supplies are compromised, your water heater may be the only clean water supply around. If sediment clogs the plastic factory drain valve, you won't be able to get to it. Thus, it's imperative that you at least replace the factory valve with a ball-valve drain assembly. To see more of our thinking on this, read our Emergency Preparedness page.

Below, you can see, top, a curved dip tube and a straight one, the latter being what usually comes with a water heater, and a brass ball-valve drain assembly, comprising plastic-lined steel nipple to fit between tank and valve, the valve itself, and a brass hose adapter.

Straight and curved dip tubes


ball valve drain assemblyy