How To Unclog A Drain Valve: The Complete Guide

How To Unclog A Drain Valve

Anthony Barnes

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Once you realize that your water heater will not drain, it can take some time to find out that it is due to a clogged drain valve.

There are ways to confirm this and it is typically from a sediment buildup that occurs inside the tank as a result of the heated water separating the mineral deposits which gradually settle down at the bottom of the water heater. 

Without regular, effective drainage, that drain valve can get clogged, the water will be trapped, and the sediment will create an inefficient water heater.

You will want to resolve this problem quickly and there are several ways to do so.

In this guide, we will look at how to check that your drain valve is clogged and the ways to unclog it.

How To Check That Your Drain Valve Is Clogged

How To Unclog A Drain Valve

Before you even begin to take some drastic measures, you should ensure that the drain valve is clogged.

There are some simple steps to take that should be done safely so you can determine if it is clogged or not without injuring yourself. 

Be careful when checking as the water in the tank may still be hot so you should wear gloves and safety goggles to prevent you from getting burned when you do drain the water heater.

Use our steps below to check if your drain valve is clogged.

Turn Off The Fuel Source

Make sure that the fuel source your water heater uses is turned off.

For an electric water heater that will be the circuit breaker while for a gas water heater there should be an on/off control knob, simply turn it off. 

Remove The Negative Pressure

Connect a regular garden hose to the drain valve then open up the valve.

Next, open one hot water faucet in your home and leave it open to eliminate the negative pressure that sits within the tank.

Check The Water

Should the water drain then turn clear, this will act as confirmation that the valve is not clogged and there may be another issue to check with a qualified plumbing expert.

However, if the water lacks pressure and trickles or does not drain at all then the valve is clogged. 

How To Cool Down The Water Before You Drain It

While you should take precautions by wearing sturdy gloves and safety goggles to prevent burning from hot water, you should want to cool the water down before draining the water heater. 

Disconnect The Fuel Source

When you do disconnect the electric or gas supply that fuels the water heater, allow it to be disconnected for a full 24 hours.

This should mean that any hot water has a chance to cool down sufficiently.

Dilute The Hot Water

While the water heater may not be clogged, you can still drain the water that remains from the drain valve and then leave the water inlet valve open.

By leaving the inlet valve open you can allow the cold water into the tank which will effectively dilute any remaining hot water and cool it down while the fuel source is turned off.

Draw The Hot Water Away

Once you have established that the water heater is clogged, open up the hot water faucets in your home, including the bathroom and kitchen.

This will draw the hot water away from the tank while you can still leave the cold water inlet open which will lower the overall temperature of the water.

Again, the fuel source should be turned off to make sure that the water does not reheat.  

Seven Ways To Unclog A Water Heater Drain Valve

You can try any of the following methods to unclog a water heater drain valve though if the first one works then, success, you can leave it like that.

However, if the first method does not work then carry on until you have managed it.

Start with the easiest methods then work your way down. 

Whichever methods you decide to use, make sure you take the recommended precautions of wearing sturdy gloves and safety goggles.

Also, double-check that the fuel source is off which means turning off the circuit breaker for electric water heaters and turning the on/off control knob to off for gas water methods.

If all of these methods fail then contact a local, qualified plumbing expert who should be able to unclog it efficiently using some specialist equipment. 

Have Some Patience

Sometimes the easiest and best policy is to simply wait it out.

Occasionally, the overall weight of the accumulated water within the tank can clear the clog and that is all it needs.

To ease it along, open the drain valve and leave it open with the hose attached.

Find the hot water faucet inside the house and close it then give it about an hour and check if the tank has begun to drain while it has unclogged itself.

Use A Wire Coat Hanger

Waiting is the easiest method as you do not have to do anything apart from giving it some time and checking it later.

A more forceful method is to use a wire coat hanger and it can be a little complicated yet should not take too much time.

Grab a bucket and some towels to catch any remaining water that may come out under the drain valve then remove the hose and close the drain valve.

Open up the drain valve then insert the wire from your coat hanger into the valve opening and move it around to loosen up any debris.

If the debris has been successfully loosened, the blockage will be unclogged and the water should flow again out of the tank. 

Keep checking the flow of water and if you are happy with it, turn the drain valve off then attach a hose to allow the tank to drain well.

As any debris or sediment moves, the valve may clog again before the tank has had a chance to completely drain.

If this occurs, you can simply grab the wire coat hanger and try it again. 

Use A Hose Stomp

Another forceful method is to use some pressure from the hose to create an air bubble.

Attach the hose to the drain valve then stomp on it while being a two feet distance away from the water heater.

This should create an air bubble to force back any sediment towards the tank to unclog the drain valve.

Just like using the wire coat hanger, the drain valve may clog again and you should try it again until the tank is drained. 

Back Flushing

The previous three methods are quite simple so you may want to try a more complicated method to unclog the drain valve.

You need a wash machine fill hose as both ends have a female connection which will prove useful.

First, close the drain valve then connect one end of the wash machine fill hose to the drain valve with the other end connected to a washtub faucet or a garden house that is connected to an outside faucet. 

To begin the flushing, turn on the water at the faucet then open the drain valve on the water heater to allow the water to flow into the tank but only for around 10 to 15 seconds.

The flushing from the water should clear the clog by moving the sediment some distance away from the valve, similar to the hose stomp. 

Once you think that the clog has cleared, turn off the faucet then close the drain valve and disconnect the hose.

To check how well the unclogging has gone, open the water heater drain valve to effectively drain the tank.

If the tank is still not draining then you may want to replace the drain valve altogether.  

Replace The Drain Valve

Backflushing and hose stomping should be able to clear a tough clogging though if they fail you can always simply replace the drain valve.

You could even replace it with the water tank being full.

First, you will need to buy a new drain valve to replace your current one and you should opt for a brass model.

Grab some Teflon tape and place some on the threads of your replacement drain valve.

Go around the house and check that all the faucets in your home are off and closed.

By doing so, you can create a vacuum in the water heater to stop the water from flowing out.

There may still be some water coming out so place a bucket and some towels underneath the drain valve to catch it to prevent you from having to clear up a substantial spillage. 

With an adjustable wrench, loosen the drain valve and take your time unscrewing it as some water may escape from the tank, even with a clog. 

Insert the new drain valve immediately which may only take a few crucial seconds then drain your tank by connecting a garden hose to your new drain valve.

If you do want to take an extra step to make sure that the clogging does not recur, use a ball valve to replace the drain valve.

Install A Ball Valve As A Replacement

How To Unclog A Drain Valve The Complete Guide 1 1

A lot of water heaters can use a cheap plastic drain valve but if you want a better solution to your clogging problem then buy a larger ball valve for your replacement.

This can help prevent a clog from sediment and it can be quite straightforward to install.

Buy a 3/4” ball valve and two 3/4” dielectric nipples which are coated in plastic while helping to prevent rust and each nipple attaches to a single side of the ball valve.

Grab some Teflon tape and place some on the thread of the nipples, the ones that will screw into your ball valve.

The ball valve’s handle should be positioned so that it opens away from the tank so you only need to place the tape on the second side of the nipples which means just three of the four threads on the nipples will have Teflon tape. 

Again, double-check that every faucet in your home is closed to create that vital vacuum to stop the water from flowing out.

In any case, put a bucket and a few towels underneath the drain valve.

Use an adjustable wrench to loosen that drain valve then slowly unscrew it as some water may flow out.

Within a couple of seconds, insert the brand-new ball valve then connect a garden hose to drain your tank. 

After it has drained, replace the ball valve with a standard drain valve or remove the handle just in case it could be opened to inadvertently drain your tank at a later date which could cause water damage.

Move The Water Heater Tank Outside

The other methods do focus on the drain valve and the final method does seem a little drastic.

You can simply move the tank outside which should make for a good excuse to replace your water heater anyway. 

First, you will need to disconnect your plumbing and the power source.

With a hand truck, roll the water heater outside then lay it on its side so the water can drain away from the very top.  

Final Thoughts

Having a clogged drain valve can cause real issues for your water heater so you will want to try to fix it as soon as possible.

There are several ways to unclog a drain valve ranging from simply giving it some time to replacing the drain valve itself. 

Whichever methods you try, always wear safety goggles and sturdy gloves as hot water can flow out.

Once you have exhausted these methods, you can contact a qualified plumbing expert and let them solve the problem for you.

Frequently Asked Questions

Which Chemicals Do Plumbers Sometimes Use To Unclog Drains?

Only a qualified plumber should use a chemical solution to unclog a drain as it can be quite dangerous if done incorrectly or without adequate precautions.

Plumbers tend to use hydrochloric acid to unclog drains and in its pure, concentrated form only licensed plumbers can purchase it from certain stores. 

Will Coke Help To Unclog A Drain?

Surprisingly yes, Coke can be used as an effective means of clearing away a blockage in your drain.

Pour a two-liter bottle down the drain and the caustic effect of the Coke can clear away a buildup.

While it is still considered caustic it is milder than most commercial drain cleaners.

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By Anthony Barnes

Anthony Barnes is the founder of Water Heater Hub and a second-generation plumber by profession. Before developing Water Heater Hub, Anthony Barnes was a full-time plumber, and he has undertaken a wide variety of projects over the decades. As a second-generation plumber, it was easy for Anthony to get used to the technicalities of all from a tender age