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.

Water Tank Drain Valve: Guidelines, Usage, Location, Repairs

Water Tank Drain Valve Location & Tank Tee

Typically the water tank drain valve is located on a brass fitting called a tank tee also showing in our page top photo.

[Click to enlarge any image]

The water tank tee is mounted at the bottom or lower side of a water pressure / storage tank where it provides the following:

• a connection for water to enter the water tank (from the well or water pump) at the right side of the tee in this photo
• a connection for the tank drain, a connection for a tank pressure relief valve,
• a mounting point for the pressure control relay possibly a connection for an air inlet valve or a water pressure gauge,
• a mounting point for a water pressure gauge
• a mounting point for a pressure relief valve (required on all pressurised tanks)
• a connection for water to leave the tank to enter the building's water piping system., at the left side of the tee in this photo

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.

Watch out: 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.

And finally, as we don't know where the end of that black garden hose (marked with a yellow question mark) terminates we have to worry that it terminates in a pool of unclean water or in wet soil - forming an un-sanitary cross connection that can contaminate the building's water supply.

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.
   
   In our photo above the white arrow points to the main water shutoff valve. When this ball-valve lever-type handle is set parallel to the water pipe the valve is in the open position.
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

• Check that the tank actually still contains water.
  
  The water tank pressure gauge may still show pressure either because the tank uses an internal bladder and the tank contains an air pre-charge or because the pressure gauge itself is stuck or debris clogged.
  
  The tank may in fact be empty. Gently rock or the tank (don't break a pipe or damage a wire). If the water tank is light it's probably empty. If the tank is heavy it may still contain water.
  
  See SHAKE the WATER TANK
  Also
  See WATER PRESSURE GAUGE ACCURACY
• Check that the tank drain valve actually opens;
  
  some valves can break internally; the handle spins but the valve doesn't open
• Check that the water tank drain hose
  
   is not kinked or that it is not draining to a location higher than the tank's outlet drain valve
• If your water tank uses an internal bladder
  
   an air pressure gauge mounted on the tank (if present) should still show some pressure when all water has left the tank: this is the air pre-charge in the tank.
  
  See WATER TANK BLADDERS for an explanation of the difference between a bladderless and an internal-bladder water tank as well as for a description of what goes wrong with the internal bladder in water pressure and storage tanks.
  
  If you cannot get water to drain from an internal-bladder type water tank:
  
  
  • Close the tank drain valve
  • Remove the tank drain hose
  • Gently open the tank drain valve enough to see if water leaves the tank
  • If water leaves the bladder-type tank then your hose was blocked or your drain valve was not open.
  • If no water leaves the bladder-type water tank and if by gently rocking or shaking the water tank you determine that it is still heavy with water, then most likely the water tank bladder has either burst and collapsed and is stuck to itself, trapping water in the tank. You'll need to replace the water tank assembly or to replace the tank bladder.
    
    See WATER TANK BLADDER REPLACEMENT
• If your water tank does not use an internal bladder 
  
  or if your system's water pressure gauge is located somewhere on the building water piping, the water system's air pressure gauge should read zero (unless the gauge is stuck - try tapping on it gently).
  
  See WATER PRESSURE GAUGE
  
  If you cannot get water to drain from a water tank that does not use an internal bladder 
  
  see the remaining water tank draining tips that follow.
• Check that your faucets are open
  
   to allow air to enter the water system
• Check that the main water valve 
  
  between water tank and building plumbing fixtures is open. (An exception to this is given next).
• Check for debris-clogging at the water tank drain valve.
  
  Particularly for bladderless water tanks but even in an internal-bladder type water tank, rust or sediment in the tank bottom can enter and clog the water tank drain valve. It might be possible to explore through the open tank drain valve with a flexible wire to feel and disturb debris, but you may have to remove the drain valve entirely if it has become debris blocked.
• To drain a bladderless water tank "uphill" 
  
  you can use low air pressure (under 70 psi) to help push water out of the tank by connecting an air source (a can of compressed air or a regulated air compressor) to the air valve on the water tank side or on nearby piping. To use pressurized air to empty a water tank you'll need to close any building faucets or plumbing fixtures or to close the main water valve between the tank and the building.
  
  Watch out: exposing any water tank to pressures higher than its rating can burst the tank and injure or kill someone.
  
  Watch out: do not use high pressure to try to empty a water tank that uses an internal bladder as you may burst the bladder or injure someone. The normal water tank air pre-charge (2 psi below the pump switch cut-in pressure) is enough to push all water out of 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 AIR 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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Reader Q&A - also see RECOMMENDED ARTICLES & FAQs

On 2020-07-30 by Milton - do you have to drain the water tank to check air pressure?

To check air pressure do you have to drain the water first?

On 2020-07-30 by (mod) - No

No, Milton, not if you only want to CHECK the pressure in the tank; and draining the water would lower the air pressure or air charge pressure in your tank.

However when you are SETTING the water pressure tank air pre-charge, YES you drain all pressure (and water) from the tank, then set the air pre-charge to 2 psi below the pump control cut-in pressure.

On 2017-01-22 by Amy - We constantly have a loss in pressure. Also our pressure switch is constantly needing repair.

We live right ouside city limits. Which puts us on a private water well. Our cistern is 2500 gallons of holding water. We run water up hill about 200 ft to the cistern. Then we run water to the house about 100 ft. We constantly have a loss in pressure. Also our pressure switch is constantly needing repair.

Fortunately, or for us right now unfortunately. We are having a lot of rain in California. So we are experiencing a bit of problems with our water. Our pump stopped working feeding our water to the house. So we again repaired the switch, the capacitor. We found that the pressure gauge from the cistern to the pump was not workig. So we put a new one on.

The pump itself has been tested to make sure it's not froze. Which it is in great working conditions. So now that we have literally gone through the electrical wiring, and the pump and bladder tank. We still can not get the pump to stop getting hot. It also doesn't stop when the switch is enabled, but gives no water to the house.

Is it my holding tank? We know that water coming out of the cistern. Just not fast. I'm assuming that there isn't a lot of pressure from the cistern itself? It comes out at about 4 gal per min or so. We haven't done a psi test on it. I'm so confused. I need water, lol who doesn't right. Can anyone help please.

On 2017-01-22 by (mod)

Based on my own decades of field experience with well pump troubleshooting, I'd first check that your pump isn't short cycling due to a loss of air charge in the pressure tank - that can burn up a pump or pump control switch

I'd next check the flow rate from the well - if your pump is pumping down the well such that it runs out of water during a pump-on cycle you need to install a well pipe tailpiece or pump protection switch to protect the pump from damage.

With that equipment in place you can pump **slowly** to fill that large water storage tank - itself a clue that you may have a low-flow well.

Question: water tank air pressure gauge stuck at 30 psi

(Dec 2, 2012) Mike said:
My system looks almost the same as above. Im trying to winterize the system. Drained and blown out with compressed air but the gauge still reads 30 psi. ?

Reply:

Mike,
If you drained the water pressure tank and piping and the gauge still shows pressure, quite probably the gauge is stuck.

Try tapping on it gently, or just replace it.

Question: Should we drain the tank to get rid of any sediment?

(Dec 4, 2012) Diane said:
We have an enormous amount of iron or minerals that stain our toilets red even though we change the filter on the water tank every two months. The water even comes out of the faucets with a red tinge. Should we drain the tank to get rid of any sediment? The water tank is approx. 12 yrs. old.

Reply:

If the stain is from iron not sediment then there may not be much sediment to drain from your water tank.

At WATER TREATMENT EQUIPMENT CHOICES you'll find articles about removing iron from the water supply.

Question: leaky drain valve at sump?

(Mar 6, 2013) Mike M said:
I recently replaced my sump pump and noticed that there is a small trickle of water flowing into the sump basin from my well water tank. It seems this shouldn't be the case. Does this mean that my valve is leaking or is this intended to stay on to relieve pressure? If it shouldn't be happening, then the sump is turning on much more often than it should, not to mention the well pump.

Reply:

(Jan 25, 2014) George Raven said:
You can drain back to the source ( well or place where you take the water)

Question: don't confuse a well water supply pump with a sump pump used to get rid of water under, in, or around a building

(Jan 25, 2014) George Raven said:
I have a well and a check valve what I did is when I shut down the pump I open a valve that bypass my check valve sending the water back to the well.
Easy

Reply:

Looks as if we are mixing up sump pumps and well pumps. Mikes sump pump needs a new check valve.
George's suggestion is interesting bit I'm a bit confused as in the case of a well with an aboveground pump his idea will lose prime.

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Continue reading at WATER TANK LIFE & REPLACEMENT or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

Or see these

Recommened Articles

• If you are having persistent water pressure problems see WATER PRESSURE LOSS DIAGNOSIS & REPAIR - home
• If you have no water pressure see WELL WATER PRESSURE DIAGNOSIS - home
• If the water pump is not working see WATER PUMP REPAIR GUIDE - home
• If the water pump runs for no apparent reason see WATER PUMP INTERMITTENT CYCLING
• If the water pump turns on and off to frequently or too rapidly see WATER PUMP SHORT CYCLING - home
• For more about the difference between water tanks and water system pressure or flow rates, see WATER TANK vs WATER PRESSURE
• WATER HEATER DRAIN PROCEDURE - if the tank you're trying to drain is a hot water heater
• WATER TANK AIR INLET VALVE - opening this valve can help in draining a water tank
• WATER TREATMENT EQUIPMENT DISINFECTION - if you need to disinfect a water tank.

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

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