Here we explain just how to drain the water out of a water heater tank. This step is a necessary first step for several water heater maintenance and repair procedures such as water heater flush-out, water heater scale removal, or replacement of the water heater pressure-temperature relief valve.

The articles at this website will answer most questions about water heaters as well as many other building plumbing system inspection or defect topics.

How to Drain a Hot Water Heater Tank

Question: Can I Drain My Water Heater Myself?

We have a gas water heater. I’m a rather handy man. Would it be possible for me to flush it myself? What is a typical cost for this kind of service? - K.S., Seattle

Reply: Sure, if you're handy and careful, it's not difficult and not many tools are needed. But

Watch out: it's easy if nothing goes wrong (we list some things that can go wrong here and

at WATER HEATER DEBRIS FLUSH. And there are a few safety things to get right: avoiding being scalded, avoiding damaging a pressure/temperature relief valve, and avoiding flooding the home because of a snafu.

Tips On Draining the Water Heater Tank: Don't try opening the hot water tank drain valve without first noting these warnings and tips:

• The water heater heat source should be turned off and the water tank cooled 
  
  down (or run hot water out through building fixtures) before attempting to drain the tank - there can be a serious scalding hazard otherwise. If someone turns on electrical power to an electric water heater that is empty, it is likely that the heater electrodes will burn up.
• You can connect a garden hose
  
   to drain the water heater tank to a suitable destination.
• Use a pony pump if you need to drain "uphill" from the hot water tank to a suitable drain location. See PUMPS, PONY PUMPS for details.
• If it's a Sunday 
  
  - you may have trouble obtaining spare parts or emergency plumbing service if a problem occurs
• Be sure to have a spare garden hose cap
  
   to install over the end of the drain valve in case it drips and won't shut off completely
• If you have trouble turning the water heater tank drain valve 
  
  to open it - don't force it - if break off the valve stem you may have a leak that you cannot shut off except by turning off cold water supply to the water heater
• After opening the heater drain valve, if you forgot to turn off the cold water supply 
  
  coming into the water heater, you may find that water just shoots out of the drain forever - you'll need to turn off the cold water supply to the water heater.
• You will probably need to open a nearby hot water tap to let air into
  
   the plumbing system and through it into the water heater tank so that water can drain out at the tank's bottom. We don't recommend opening the pressure/temperature relief valve for this purpose as you may find that the TP valve won't shut successfully afterwards. Details about letting air into the water tank so that water can drain out are at WATER HEATER AIR INLET.

More details about draining and cleaning or de-scaling a hot water tank, including the removal of mineral or lime deposits and silt, are provided at WATER HEATER NOISE DIAGNOSIS, CURE where we describe water heater flushout and water heater scale removal.

If plastic water piping is installed, 

such as polybutylene water supply piping, it should be at least 18" from the water heater.

Water heater vacuum relief valves

 are required at water heaters in some communities, to protect against collapse of the water storage tank and to prevent backup of hot water into the cold water piping should cold water pressure drop. Here is Carson Dunlop's sketch of a vacuum relief valve.

What Goes Wrong When Draining the Water Heater Tank?

Watch out for these common problems that occur when you try to just drain a hot water heater tank:

Don't forget to turn off water coming into the water heater tank or you'll certainly never get it drained.

The water heater tank drain valve may be defective,

 may fail to open, or may fail to shut off, or worse, may break so that water comes blasting into the room where the heater is located. If this happens you will have to be able to turn off cold water coming into the water heater, and even so, water that is in the water heater tank and in building piping above the heater will drain backwards through the heater and onto the floor. Don't force any parts, especially parts on a plastic water heater drain valve.

Water heater tank drain valves are a pretty standard plumbing part. If your valve is worn or damaged, or if you just want to be extra safe, buy a replacement valve at a lumber or hardware supplier before starting your project. Most valves are standard 3/4" male pipe thread. You'll also need teflon tape or teflon pipe dope for the pipe threads.

The water heater cold water supply valve may not shut off:

especially as that valve may not have been used for quite some time. Or you may not be able to turn the valve. Do not force the valve - you may break it. Sometimes we can loosen a recalcitrant water shutoff valve by a combination of a little squirt of WD-40 or a spray used by mechanics to free frozen nuts and bolts. Don't get these chemicals inside the water heater.

If your water heater supply valve won't turn off fully and is just dripping into the hot water tank, you can live with that during a water heater drain and repair project. If the valve won't turn off at all, you may have to turn off another supply valve upstream from the water tank, or possibly you'll need to turn off water supply to the whole building before starting your project.

If you run into trouble you won't want to have to leave the whole building water supply shut down, so having a few spare parts on hand to be able to close off the water heater itself (relief valve, tank drain valve) may be necessary.

The water heater relief valve may leak:

often we use the test lever to allow air into the water heater tank during draining, as that will speed up the water heater tank drain process.

Watch out: But lifting the test lever can allow a bit of debris or even a damaged relief valve seat washer to flow out.

At WATER HEATER DEBRIS FLUSH we discuss dealing with this problem.

Where should the water heater draining garden hose drain-to?

 If you are routing a water heater drain hose to an indoor floor drain, be sure that drain is not clogged before beginning the project. Try pouring a bucket of water into the drain. If you are routing the water heater drain hose to outdoors, the water leaving the water heater tank should empty far enough from the building that it won't leak back into the structure through the foundation wall.

At WATER HEATER DEBRIS FLUSH we discuss dealing with this problem.

Question: no house water after replacing a water shutyoff valve and draining the hot water tank

(Mar 2, 2014) Anonymous said:

water shut off valve has been replaced after breaking. the hot water tank drained and i hooked water supply back to tank. now i get zero water in the house, but my water meter is sppining very slow

Reply:

Anon: water meter spinning argues that there's a leak on the house side of the meter, or water is passing into the building and maybe a toilet is running; Yet you see "zero water" - you can start checking by turning off water at the main and looking at the meter to see if it stops; also if there are shutoffs that isolate different building areas those can narrow down the problem.

Finally, if the new water shutoff valve was installed using soldering and too much solder was pushed into a joint that could have blocked the valve. And of course, Make sure the valve is opened in the right direction.

This series of water heater maintenance and repair articles describes how to inspect, operate, diagnose, and repair electric hot water heaters.

• To drain your water heater tank, for example to replace a part,
  
  see WATER HEATER DRAIN PROCEDURE
• To flush accumulated crud or debris from a water heater (yearly maintenance)
  
  see WATER HEATER FLUSH PROCEDURE 
• To de-scale or de-lime your hot water heater,
  
  see WATER HEATER SCALE DE-LIMING PROCEDURE
• To diagnose and repair a bad water heater dip tube or anode,
  
  see WATER HEATER ANODES, DIP TUBES
• To diagnose particulate debris in the building water supply, faucet strainers, etc. that comes from the hot water tank, and how to fix that problem,
  
  see WATER HEATER DEBRIS FLUSH
• To sanitize or disinfect a water heater
  
  
  see WATER TREATMENT EQUIPMENT DISINFECTION

...

Continue reading  at WATER HEATER FLUSH PROCEDURE or select a topic from closely-related articles below, or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

Or see these

Recommended Articles

• WATER HEATER AIR INLET for help in speeding the water tank or water cylinder drain process

Suggested citation for this web page

WATER HEATER DRAIN PROCEDURE at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

Or see this

INDEX to RELATED ARTICLES: ARTICLE INDEX to WATER HEATERS

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