The short answer
Tap water in Northern Virginia is moderately hard to hard. The minerals in it settle on the bottom of your water heater, the burner or elements have to heat the water through that layer, and over time the tank starts to rumble and pop. Draining and flushing the tank pulls the sediment out.
The part most people don’t know
In a 2010 study run by Battelle for the Water Quality Research Foundation, gas tank water heaters lost 4 percent of their efficiency for every 5 grains per gallon of hardness when the house used 50 gallons of hot water a day, and 8 percent per 5 grains at 100 gallons a day. At the extreme, 30 grains and 100 gallons a day, the loss hit 48 percent. Electric tanks built up as much as 30 pounds of rock-like scale. Tankless units on 26 grain water stopped working after the equivalent of 1.6 years.
Two caveats. The foundation is the research arm of the Water Quality Association, the water treatment trade group, so the study is industry funded. And the test was sped up on water far harder than ours. Read it as a direction, not a forecast for your basement.
$99 Water Heater Flush
We drain and flush the tank, check the anode rod and test the relief valve, then go through the house's plumbing with photos, included. See the flush
Want your own number before anyone comes out? The water heater estimator prices your house in a few questions.
How hard is the water here?
Each water system publishes its own numbers. The USGS scale calls 61 to 120 milligrams per liter moderately hard and 121 to 180 hard.
Swipe to see all columns →
Swipe to see all columns →
| Water system | Hardness |
|---|---|
| Fairfax Water | 5 to 10 grains per gallon (84 to 170 mg/L), moderately hard to hard |
| Loudoun Water (2011) | 4.9 to 9.9 grains per gallon, moderately hard to hard |
| Prince William Water, East and West | 3.5 to 7.0 grains per gallon, moderately hard |
| Prince William Water, Bull Run Mountain, Evergreen, Hoadly Manor | 7.0 to 10.5 grains per gallon, hard |
Our rough math on the study’s numbers: a gas tank on 5 to 10 grain water, using 50 gallons of hot water a day, would lose somewhere around 4 to 8 percent of its efficiency if nothing is ever done about the scale. That’s arithmetic on their figures, not a measurement of your tank.
How sediment shows up
- Rumbling or popping. Rheem’s gas water heater manual lists a rumbling noise, cause scale and sediment in the tank, fix clean the tank. Here’s what each water heater noise means, and our sediment video shows what comes out.
- Less hot water, slower recovery. A.O. Smith says sediment and lime buildup can reduce a water heater’s efficiency, and heavy deposits can damage the heater.
- A worn anode rod. A.O. Smith calls the anode a sacrificial metal rod that helps prevent corrosion and leaks in the tank. DOE’s water heater guide says inspect it every three to four years.
How often to flush
The advice varies by who’s giving it. DOE’s guide says flush a quart of water from the tank every three months and check the temperature and pressure relief valve every six months. A.O. Smith says drain and flush after the first six months to see how much sediment builds up, then once a year, or more often if there’s a lot. Bradford White says drain off a gallon every month. Most homeowners do none of it. Here’s water heater maintenance in Northern Virginia, and if yours is already acting up, what water heater repair usually involves.
What we check
Our water heater flush is $99: we drain and flush the tank, check the anode rod and test the relief valve, then go through the house’s plumbing with photos, included. If the tank is the problem, our water heater estimator shows your installed price first, then $500 comes off a new water heater, any size, replaced by our own plumbers.
Water heater showing a code or a blinking light? Our error codes and warning lights guide covers what each one means.
Book it
Book the water heater flush, call (703) 997-9757, or book online from goswiftpro.com/cookiesoffer and a box of warm cookies comes with the visit. Rated 5.0 stars across 1,138 reviews on Google, Angi, Yelp, the BBB and Facebook, Virginia Class A license 2705192276.
Questions people ask
How do I know if my water heater has sediment?
Rumbling or popping while it heats is the classic sign; Rheem’s manual lists scale and sediment as the cause. Less hot water than it used to make is another clue.
How hard is the water in Northern Virginia?
Moderately hard to hard. Fairfax Water reports 5 to 10 grains per gallon, Loudoun Water 4.9 to 9.9, and Prince William Water 3.5 to 10.5 depending on the system.
How often should I flush my water heater?
DOE says flush a quart every three months. A.O. Smith says drain and flush after six months, then once a year or more often if there’s a lot of sediment. Bradford White says drain a gallon every month.
Does sediment make a water heater less efficient?
Yes. A.O. Smith says buildup reduces efficiency and heavy deposits can damage the heater. An industry funded 2010 study found gas tanks lost 4 percent efficiency per 5 grains of hardness at 50 gallons a day.
