Water heater tank flushout - how to let air into the water tank: Here we explain methods to allow air to flow into the hot water heating tank during a water tank drain procedure. Without this step you may find it difficult to drain down the water heater.

We discuss how to use the pressure/temperature relief valve to let air into the water heater to make draining easier, and we describe how to fix a dripping or leaky pressure relief valve or how to replace the pressure/temperature relief valve if necessary.

How to Let Air Into the Hot Water Tank to Speed-up Water Tank Draining or Flushing Procedures

• 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

The articles at this website will answer most questions about diagnosing and curing noisy domestic water heaters and about the procedure to remove mineral deposits, lime, water scale, silicates, sulfates, aluminates, or silt and sand from a water heater tank.

Warnings Before Starting to Work on a Water Heater

Watch out: draining and flushing out a residential water heater is pretty easy and only a few common hand tools (adjustable wrench) are needed. But it's only easy if nothing goes wrong.

A stuck or broken control valve or drain valve, or difficulty finding how to drain water out of a basement-located water heater with no nearby floor drain can all present challenges during the drain operation, and there can be a few surprises when you are putting things back together too: a leaky water heater drain valve or leaky water heater relief valve.

See DRAIN a WATER HEATER TANK This article describes dealing with the more common of these water heater tank draining troubles: defective water heater tank drain valve, water heater cold water-in supply valve won't operate.

Our standard water heater drain procedure for flushing out mud, silt and crud as part of regular heater maintenance is

at WATER HEATER FLUSH PROCEDURE.

See WATER HEATER DEBRIS FLUSH for a detailed photo guide through draining and cleaning out a water heater that had been sending debris into the building water supply piping.

Watch out: Safety Warnings: don't tackle this water heater cleanout project on a Sunday night when you can't call a plumber or buy a replacement part. Water heaters, their heating source (oil or gas burner or electricity or solar hot water), and particularly their relief valves include critical safety components. Do not modify or remove relief valves, chimney connections, draft hoods, etc. as you may create dangerous conditions.

You'll find that just opening the tank drain doesn't do a thing unless there is a way to get air into the water heater tank as water is running out.

• Open a nearby faucet,
  
  or as some manufacturers recommend, remove the pressure/temperature relief valve from the water heater tank to let air into the tank and speed the draining process.
  
  Notice that the manufacturers say to remove the relief valve? You could just use that test lever on the valve to open it. Manufacturers don't want you messing with that lever because their experience, and ours, is that on occasion the valve will continue to leak after the lever has been moved. That's what happened to us. Below we describe the problem, what repairs we tried, and what finally worked.
  
  Watch out: you cannot remove the water heater TP relief valve before the water level in the tank has dropped below the mounting point of the valve on the tank top or near the tank top on the side of the unit. Otherwise water will just pour out of the relief valve mounting hole and all over the floor.
  
  Watch out if the water in the water heater is hot you can be scalded.
  
  Removing the relief valve may also let combustible hydrogen gases formed during deliming (if you use a deliming chemical) vent out of the tank. Soak the relief valve in delimer or in vinegar if its sensor or other components are coated with mineral deposits, or simply replace the valve with a new one (to be extra safe) of the same rating.
  
  When the water heater tank has been fully drained, remove the drain valve and inspect it for clogging or damage - clean or replace the drain valve as needed.

How to Let Air Into the Hot Water Tank to Speed the Tank Draining Process

This article explains using or removing temperature and pressure relief valves on residential water heaters to let air into the hot water tank during draining for cleaning or other purposes. For more details about water heater safety valves

see RELIEF VALVE, WATER HEATER and for a discussion of temperature and pressure relief valves used as safety devices on heating boilers please

see RELIEF VALVE, TP VALVE, BOILER.

It is possible to speed the heater draining and also to ease the flushing procedure if you open a hot water tap nearby so that you can let air into the heater as water leaves it

Some plumbers open the water heater pressure/temperature relief valve for this air-in purpose - but there is risk that you'll later be unable to get the valve to shut fully again - debris can clog the valve seat - sometimes we can stop a relief valve from dripping by tapping on the valve lift rod that protrudes through the valve lift lever

Other plumbers simply remove the relief valve entirely - this is the process recommended by some water heater manufactures such as A.O. Smith. Removing the relief valve makes it easy to inspect this critical safety component itself, and it's easy to clean or replace the safety valve at that time.

When replacing the relief valve use an approved teflon tape or pipe sealant and work neatly and with care so that there will be no leaks at this location.

Safety Warning- a damaged, improperly-selected model, or modified pressure/temperature relief valve is dangerous and could lead to a serious BLEVE explosion should the water heater later overheat.

Notice that the manufacturers say to remove the relief valve?

You could just use that test lever on the valve to open it. Manufacturers don't want you messing with that lever because their experience, and ours, is that on occasion the valve will continue to leak after the lever has been moved. That's what happened to us. Below we describe the problem, what repairs we tried, and what finally worked.

Watch out: you cannot remove the water heater TP relief valve before the water level in the tank has dropped below the mounting point of the valve on the tank top or near the tank top on the side of the unit. Otherwise water will just pour out of the relief valve mounting hole and all over the floor.

Watch out: if the water in the water heater is hot you can be scalded.

Removing the relief valve may also let combustible hydrogen gases formed during deliming (if you use a deliming chemical) vent out of the tank. Soak the relief valve in delimer or in vinegar if its sensor or other components are coated with mineral deposits, or simply replace the valve with a new one (to be extra safe) of the same rating.

When the water heater tank has been fully drained, remove the drain valve and inspect it for clogging or damage - clean or replace the drain valve as needed.

The Temperature/Pressure Relief Valve is Leaking on my Water Heater - Now What?

OK so we told you so.

If the TP valve is leaking because the temperature or pressure are too high, it's doing its job.

See RELIEF VALVE, WATER HEATER for details about how TP valves work, why they leak, how dangerous leaks or malfunctioning valves may be.

But more likely, even though we told you not to, you tried messing with the test lever, you left it in the "open" position as a quick easy way to let air into the water heater tank. To be honest, we do this too.

But we never ever touch that lever unless we are prepared to either leave the water heater shut off entirely OR we are prepared to go buy and install a new TP valve.

Here are some things to try if the TP valve is just dripping:

Tap gently on the rod that protrudes through the test lever and that would be pulled (against an internal spring) when you lift the lever. Sometimes a gentle tap will seat the valve and it'll stop leaking.

Watch out:  Tap GENTLY. If you bang on it and damage the valve or seat or internal washer, the leak will get worse.

Lift the valve and flush the valve seat. That's what we tried recently when our TP valve was leaking after draining the water heater.

That heater tank had a lot of floating debris particles and we had the fantasy that we could flush the valve seat and it'd stop leaking. It didn't work.

Watch out: The risk too is that if the internal TP valve washer is in poor shape, you may blow out the washer or part of it when you open and flush the valve, making the leak worse. We lifted, flushed, then tried the tapping trick again. It didn't work. The water heater was cold so we knew this wasn't an overheat or overpressure problem.

Put a bucked under the valve extension tube so we don't flood the floor.

Watch out: But do NOT accept this as a remedy. If you leave the valve leaking it may eventually stop leaking due to build up of mineral deposits from the hot water passing by. Then you have no working TP valve and there is a risk of water heater explosion.

Replace the TP valve with a new unit. That's what we had to do in the system discussed

at WATER HEATER DEBRIS FLUSH. The valve dripped on the floor over the weekend until the owner bought a replacement TP valve.

Here are Detailed Steps in How We Replaced a Water Heater Temperature/Pressure Relief Valve

• Cool down the water heater by turning off the burner and running "hot water" in the home until it came out cool
• Turn off water supply to the water heater.
• Drain enough water out of the water heater so that water level is just below the level of the TP valve where it mounts on the tank. If you're not sure, and since you're going to replace this valve anyway, you might try opening it with the test lever - if no water comes out, maybe the water level is low enough - provided the valve opens at all.
• Remove the TP valve extension tube - set it aside for re-use
• Remove the TP valve by unscrewing it from the water heater - counter-clockwise is "unscrewing" - it may take a big wrench if the valve is stuck or glued in place.
  
  Watch out: for breaking off a valve or stripping threads in the mounting opening on the water tank - that could lead to complete water heater replacement.
• Compare the data tags on old and new Temperature Pressure relief valve to be sure we've bought the right item - the valve must have adequate BTU, temperature response, and pressure dumping capacity or the water heater will be unsafe.
• Prepare the new TP valve threads with teflon tape or teflon pipe dope.
• Screw in the new TP valve carefully, ending with the valve pointing downwards if it's mounted on the side of the water tank.
  
  Watch out: don't over-tighten the valve - you may end up with the valve fully tight but not pointing down. Just backing it off might lead to a leak. If you make this mistake remove the valve, re-wrap with teflon tape and start over. We always use the smallest wrench that will work when installing threaded parts in order to avoid damaging something.
• Restore the TP valve extension tube
• Refill the water heater
• Turn the water heater back on.
  
  Watch out:  do not turn on an electric water heater with no water in the tank - it'll be destroyed.
• Check for leaks - don't mistake a few drops of water left in the extension tube for a leak - water may have been in the tube from the prior leaky valve.
• Check again in 24 hours for leaks at the end of the extension tube.

That's it.

If you \were dealing with water heater scale and lime, after flushing out the water heater tank, the second step in curing water heater noise or insufficient hot water is to remove scale or lime from the water heater tank. If the unit is an electric water heater, you'll also need to remove scale from the electric water heater elements.

...

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

Or see these

Recommended Articles

• WATER HEATER SCALE DE-LIMING PROCEDURE or the full article on the detailed procedure for removing lime and water heater scale.
• WATER HEATER DEBRIS FLUSH

Suggested citation for this web page

WATER HEATER AIR INLET 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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