Low Hot Water Pressure

Low hot water pressure is usually caused by sediment, rust, calcium deposits or other debris in the plumbing lines or faucets.

This often occurs after the plumbing has been worked on, water heater replaced etc.

Sometimes the pressure will slowly decrease over a period of time, particularly if your home has been plumbed with galvanized pipe.




If you have just moved into a house with low hot water pressure take a look at the plumbing going into and out of the water heater. If it has been plumbed with 1/2 in. pipe going in or coming out you will not get as much pressure as you could if it were plumbed properly.

Corrosion and rust will slowly clog galvanized pipe. There's not much you can do about this except replace the pipe, however it is worthwhile to check your aerators and faucets. Just follow the guide below.


Low hot water pressure in part of the house


Sink faucets

Clogged Aerator on kitchen sink faucet

A clogged aerator is the most likely cause of low hot water pressure in a sink faucet.

Remove the aerator with a pair of pliers (see pic).
Tap it on the counter top and the inside parts will come out.
Give it a good cleaning, put it back together and reinstall it.

Now check the hot water pressure. If cleaning the aerator didn't help go to the next step.


Faucet stem clogged, remove handle

You may have a clog in the faucet itself. This is an easy fix.

Turn the hot water off under the sink. Use a knife to pry up the ID button on the hot side faucet handle.
Remove the screw holding the handle. Remove the handle.


Remove stem retainer nut

Unscrew the stem retainer nut and pull straight up on the stem, it should pop out.

The stem may have a washer mounted on the bottom of it. If not there will be a washer and spring inside the faucet housing.

Gently remove the washer and spring with a small screwdriver.


Remove stem, flush debris ftom faucet

While holding a cup or glass over the faucet turn the hot water supply on and off several times.
This should flush out any debris stuck in the line.
Reassemble the faucet and turn the water on and check the pressure.

If you still have low hot water pressure the problem may be the supply line under the sink.
Remove the line from the shut-off valve and the bottom of the faucet and clean or replace it. Also check the pressure coming out of the shut-off while you have the supply line off.


Single handle faucet

Turn both the hot and cold water off under the sink.
Remove the handle.
Loosen and remove the retaining collar.
Pull the ball cartridge out.
Remove both washers and springs from the faucet.
Place a glass or cup over the faucet and turn the hot water on and off several times. Its a good idea to flush the cold side while the faucet is apart.
Reassemble the faucet and turn the water on.


Low pressure in the bathtub and shower

If you have low hot water pressure in the shower only and not in the tub remove the shower head with a pair of pliers.
Look into the back side of the shower head.Pry out any parts you see with a small screwdriver and clean everything.

If you have low pressure in the tub faucet it will disassemble much the same way as the other faucets.
If you have a two handle tub faucet you can cut the hot water off at the water heater. Only remove the hot side stem.

On a single handle faucet you'll find a screw on each side of the faucet body after the large chrome cover is removed. Screw both of these in tight before you remove the stem. If you can't see them (sometimes builders cover these up) you need to cut off the main water supply to the house.

When you have everything removed from the faucet turn the water on and off several times to flush out all debris.
Reassemble the faucet and give it a try. Don't forget to clean the shower head if you haven't already.

Low water pressure in the clothes washer

The water inlet valve on the back of your washing machine where the water hose is attached, has a screen to catch debris before it enters the machine.

Cut the water off behind the washer. Remove the hot side hose. Carefully pry the screen out with a small screwdriver. Clean the screen and reinstall.
Some washing machine hoses have screens in them also.


Whole house low hot water pressure

To solve this problem we'll have to start at the water heater and eliminate possible causes one at a time.
Water can only come out of a water heater as strong as it comes in. If you have a 3/4 in. copper or cpvc pipe bring water into the water heater and 3/4 in. leaving the water heater and your cold water pressure is strong you should have good hot water heater pressure.

If you have older galvanized pipe or any 1/2 in. pipe entering or leaving the water heater you will not be able to get great hot water heater pressure.


Check water heater fill tube and shut-off valve

The water heater shut-off valve should be located on the cold water line near the water heater.

Check the valve to be sure it is opened all the way.

The next step is to see if you have the proper pressure going in and coming out.
If you're water heater has flex supply lines (copper or silver colored) with a large nut at each end this check will be easy.

If your water heater is plumbed with copper or cpvc you'll have to cut the lines and remove the fittings from the water heater. If the plumbing is not attached to a nipple at the heater you will need to get a 3/4 in. nipple to screw into the water heater so you can attach a garden hose to it.

Turn off the water supply to the water heater. Grab your wife's mop bucket and drain about 1/2 gal. of water out of the heater.
The water heater drain valve is located at the bottom of the heater.

Remove the flex line from the hot side (where the hot water comes out of the water heater) of the water heater.

Take a flash light and look down the nipple where you took the flex line off. If you see a lot of build-up in the nipple you've found the problem.
Don't try to clean the nipple this will just cause more problems later.
Replace the nipple with a dielectric nipple. The inside of these nipples are coated in plastic to cut down on rust.

If you don't see a problem at the nipple attach a garden hose to the nipple and run the hose outside. Make sure its not kinked anywhere.
Turn the water on at the water heater. Go outside and see how strong it is running.
You should have about as much pressure as you would have coming out of an outside faucet if you attached a hose to it.

If the pressure is good you have eliminated the water heater as the source of the problem.
The problem will be between the water heater and the faucet nearest the water heater(if the faucet has low hot water pressure). My guess would be a restriction in an elbow somewhere in the line, maybe near the water heater.
At this point the only thing to do is open the water line at the sink and clean the line back to the water heater with a snake. Should you try it? I don't recommend it. The snake could get hung in the line. Never try this if you have galvanized pipe.

If the pressure is not good coming out of the water heater you'll need to check the pressure coming into the water heater. This will involve checking the cut-off valve and the water heater dip tube.


Open water heater supply valve completely

The cut-off valve or gate valve that controls the water supply to your water heater can malfunction and cause low hot water pressure

There are a couple of ways to check the gate valve. Choose the one that's easiest for you.

Shut the water off to your house, remove the top of the gate valve,check that its working properly and for any obstructions.

Detach the flex line on the cold water side. Screw a 3/4 in. nipple into the end and attach a garden hose to the nipple. Run the hose outside, turn the shut-off valve on and check the water pressure.


Removing water heater fill tube

It's possible that the water heater fill tube has clogged. To check it, remove the water supply line on the cold side of the water heater. Remove the nipple if there is one.

The fill tube is a plastic pipe with a flange at one end to hold it in place. To remove it insert your finger into the pipe. Wiggle your finger to loosen it and pull it out.

You will see a small hole in the fill tube about 6 in. from the end. It's suppose to be there.


Fill tube may be clogged

This is a fill tube that I removed from an old water heater behind my shop.

While you have the fill tube out of the water heater check it for cracks. Replace it if you find one.


If you have copper plumbing it can be a pain to cut it loose. You can check your fill tube another way.
Attach a garden hose to the water heater drain valve and run it outside. Turn the drain valve on and check the pressure coming out. If the pressure is equal to an outside faucet the cut-off valve and fill tube are ok. If the pressure is low you will need to drain the tank, remove the drain valve and check it to be sure its not clogged. Reinstall it, fill the tank and open the drain valve again.
If you are sure the drain valve is not clogged and the pressure coming out the hose is low then the problem will be incoming water pressure.

Other causes of low hot water pressure

If you have a water softener by pass it and check your pressure.

A water leak can cause loss of pressure. If your house is on a concrete slab walk around the house and look for a wet spot. Put your ear to the floor in the kitchen and bath. You may hear water spraying. This really works!

To eliminate future low hot water pressure problems. It's a good idea to flush your water heater every three months. flush hot water heater

Clean your water heater at least once a year. cleaning hot water heater






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