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Photograph of a water pressure tank air valve Water Tank Drain Valve Location & Repair
How to Drain a Water Tank

  • WATER TANK DRAIN VALVE - CONTENTS: Water tank drain valve information: where do we find the water pressure tank drain valve on a private well, tank, and pump system, how is it used, how to repair leaky valves. How to drain a water tank or water pressure tank.
  • What are the controls, switches, valves found on water tanks and water pumps, what do they do, how are they repaired?
  • POST a QUESTION or READ FAQs about drain valves on water pressure tanks / water storage tanks
  • REFERENCES
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Water storage tank drain procedure & water tank drain valves:

Where do we find the water pressure tank drain valve on a private well, tank, and pump system, how is the water tank drain valve used during water tank service or repair, and how we replace or repair leaky drain valves.

How to get water out of a water pressure tank or water storage tank. Step by step procedure for draining a water tank and steps to return the water tank to service after draining.



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WATER TANK DRAIN VALVE Guidelines, Usage, Location, Repairs

Photograph of a sketch of the main controls and valves on a water system

Article Contents:

[Click to enlarge any image]

Water Tank Drain Valve Location & Tank Tee

In the page top photo you can see a round black handled drain valve in the center of the picture, just below the pressure gauge. This valve is used to completely drain the water tank (and possibly the entire water piping system too).

Photograph of a water pressure tank air valveTypically the water tank drain valve is located on a brass fitting called a tank tee also showing in our page top photo: the water tank tee is mounted at the bottom or lower side of a water pressure / storage tank where it provides a connection for water to enter the water tank (from the water pump), a connection for the tank drain, a connection for a tank pressure relief valve, possibly a connection for an air inlet valve or a water pressure gauge, and a connection for water to leave the tank to enter the building's water piping system.

Usually when a water tank drain valve is to be opened the water tank drain is connected to a hose which is run outside of the building or to a nearby floor drain.

This water tank drain is not normally opened when the pump is turned on since you'll simply run the pump and flood the building, but we have used it as a convenient way to connect a water hose to the system. We once put out a small fire in this manner.

Water tank drains should be piped to a visible location: not installed with a drain to a crawl space as this owner did. For convenience, the owner wanted to be able to drain the water system to avoid freezing when this home in Rhinebeck New York was unoccupied.

But first of all, sending water into the crawl space risks mold, rot, and insect damage to the building, and second, it's generally a bad idea to send any drain, overflow, or relief valve to a hidden location. If the piping is leaking we want to know it.

If the water tank drain is leaking it needs to be repaired (usually a simple internal washer) or replaced.

But you can defer this repair by screwing a garden hose cap onto the gauge threaded outlet. We put these caps on all of our tank drains in areas where children are playing since on occasion they've been opened by curious kids.

Procedure for Draining a Water Pressure Tank

  1. Turn off the water pump or well pump. Usually this is accomplished by an electrical switch that powers the well pump, usually located close to the pump; if you can't find that switch turn off the pump circuit breaker or fuse.
    Watch out: do not touch electrical equipment if standing on or in water. You could be shocked or killed.
  2. If there is a shutoff valve between the water tank and building, open it. Most water systems include this valve, on piping between the water pressure tank and the building water supply system piping. The valve is usually close to the water pressure tank.
  3. If there is a shutoff valve between the well piping and the water pump, close it. This may help avoiding loss of well pump prime as we discuss below. This valve may not be present on your system as most well and pump systems use check valves but no shutoff valve between the house and well piping. This valve is more likely to be present if your water pump and pressure tank are functioning as a water pressure booster for a municipal water supply system.
  4. Connect a drain hose. If necessary to prevent spilling water where you don't want it, connect a garden hose to the water tank's drain valve and run the other end of the hose to a suitable drainage location. Ideally the drain hose should slope down continuously from the point of connection to the water tank, but if your hose has to run uphill and then down, as long as the "down" portion of the hose is longer than the length of hose between the water tank and the hose high point you'll still be able to drain the water tank by gravity. The longer downhill hose length will help siphon water out of the tank.
  5. Open the drain valve at the water tank to which you connected the drain hose
  6. Open one or more nearby plumbing fixtures such as a sink or tub faucet to allow air to enter the piping and water tank system. Without allowing air into the system you won't be able to drain all of the water out of the water tank.
  7. Wait for water leaving the water tank to stop. At this point the tank should be empty. Gently rocking the water tank (taking care not to break or disturb a plumbing or electrical connection) can sometimes help confirm that the tank is empty.

If you are unable to get all of the water to drain from the water tank

How To Restore a Water Tank (and pump) to Service After Draining

  1. Close the water tank drain. You can also remove the drain hose at this point. Quickly lift up the removed end of the drain hose that you'd connected to the water tank drain to help assure that any water remaining in the hose drains to outside rather than backwards onto the floor at your water tank.
  2. Check or set the water tank air pressure pre-charge.

    For a bladderless water tank that you emptied completely of all water, no air pre-charge will be needed to return the tank to service and adding air will simply push that air out of nearby faucets. If you did not fully drain the water tank
    See WATER TANK AIR, HOW TO ADD

    For an internal-bladder type pressure tank that is empty the air pre-charge is set to 2 psi below the pump control switch cut-in pressure.
    See WATER TANK PRESSURE ADJUSTMENT for tanks that use an internal bladder
  3. Close building faucets that you opened to allow air to enter the piping and tank system to aid draining the water tank
  4. Close the main water valve between the water pressure tank and building water piping
  5. Open the water valve between pump and well piping (or municipal supply piping if this is a water pressure boosting system) if one is present.
  6. Turn on electrical power to the water pump.

    Watch out: if your well pump has lost prime you should not allow the (above ground) water pump to run dry as that can damage the pump leading to costly repairs. A faulty foot valve or leaks in well piping or other problems can cause loss of well prime.
    See WATER PUMP PRIMING PROCEDURE
  7. Wait for the pump to stop: the water pressure should rise to the water pressure control switch cut-off pressure (typically between 40 and 70 psi) in a few minutes (less than 5 unless you are using a very large water storage tank system). If the well pump keeps running and never reaches the cut-off pressure, then
    See WATER PUMP WONT STOP RUNNING
  8. Open the main water valve between the water tank and the building.
  9. Open one by one each faucet to purge any excess air from the building piping & water system. These are the faucets that you had previously opened to let air into the piping system to drain the water tank, then had closed for this step. You will probably see air discharge at the faucet that you open. Leave water running until the air discharge stops. If air discharge continues more than a minute there may be a separate problem.
    See AIR DISCHARGE at FAUCETS, FIXTURES

    The pump may turn on during this process depending on the volume of water necessary to remove all of the air from building piping.
  10. When the air purge is complete at each fixture close the fixture valve. The pump may run for a brief period but should stop. If the pump does not stop and all valves are closed,
    See WATER PUMP WONT STOP RUNNING

Your water system should now be operational. What else might be wrong?

In an emergency if your building has lost water pressure but a neighbor's water system is working, you can "back feed" your building's water piping by connecting a garden hose from your neighbor's outside water faucet to this water tank drain.

You'll need a double-female-ended washing machine hose to complete the connection. Of course you could back-feed from a neighbor to any easily accessible hose connection on your building such as an outside water spigot or a washing machine cold water hookup as well.

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Continue reading at WATER TANK REPLACEMENT or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES below.

Or see WATER TANK AIR INLET VALVE - opening this valve can help in draining a water tank

Or see WATER HEATER DRAIN PROCEDURE - if the tank you're trying to drain is a hot water heater

Or see WATER TANK: USES, TROUBLESHOOTING - home

Or see WATER TREATMENT EQUIPMENT DISINFECTION if you need to disinfect a water tank.

Suggested citation for this web page

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

INDEX to RELATED ARTICLES: ARTICLE INDEX to WATER SUPPLY, PUMPS TANKS WELLS

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