Low Hot Water Pressure? Here is Why and What to Do

Why is My Hot Water Pressure so Low?

Low water pressure in the house is very frustrating. It is even more frustrating when the low water pressure is only affecting the hot water faucets or outlets while the cold water pressure is perfectly fine.

But what causes low hot water pressure in the house while the cold water pressure is as it should be? And what can you do to fix it?

Low hot water pressure in the house is mainly caused by sediments in the hot water system clogging up the hot water supply pipes and fixtures, restricting the flow of water. It could also be caused by partially opened shut off valves, clogged water filters and leaking pipes

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If you have low hot water pressure in your upstairs, you are most likely dealing with air lock in the hot water pipes. Flushing the water heater will in most of the times fix the problem.

The first thing to do when you notice that low hot water pressure in your house is to determine if it is affecting just one fixture or the entire house. It is easier to fix low hot water pressure in a single fixture than the whole house.

Low hot water pressure in the shower is caused by a partially opened shut off valve or an anti-scald device that has been set to high. It could also be as a result of a dirty/clogged faucet cartridge.

Low hot water pressure in the kitchen or bathroom faucet is caused by clogged or kinked water supply hoses. It could also be that the hot water shut off valve under the sink is partially opened or clogged as well.

To fix low hot water pressure in the shower, check out this post. If on the other hand the low hot water pressure is only affecting the kitchen or bathroom sink, check out this post.

How Do You Fix Low Hot Water Pressure?

If you have determined that indeed the low hot water pressure is affecting the whole house, it is time to move forward and fix the problem. Some things you can fix on your own while others will need you to call in a licensed plumber.

Here are the different ways to increase the hot water pressure in your house:

1. Check for Leaks

The very first thing to do is to ensure that there are no leaks. Leaks in the house can lead to even more expensive repairs if not noted and fixed in good time. So, how do you know if there is a water leak in your house?

  • Monitor your water meter – The water meter shows the amount of water flowing in your property. To see if there is a leak in one of your pipes, turn off all the faucets and fixtures including dishwasher and washing machine. Check if the water meter is still running even with everything turned off. Note that a slow leak will not be noticeable immediately. Monitor it for 2 hours. If the meter changes know that you have a leak in one of your hot water pipes.
  • Look for damp walls and ceilings – Damp walls and ceilings are tell-tale signs of a water leak.  Be careful as sometimes this can be caused by a leaking toilet upstairs.
  • Hot water pooling/leaking – If one of your fixtures have a leak, water will pool on the floor. Check under your kitchen/bathroom sink cabinets or shower/bathtubs for the same.

If you notice any leak please turn off the main house shut off valve immediately and call a plumber. Water leaking from a pipe can cost thousands of dollars in damage repairs.

2. Drain and Flush the Water Heater

Problems associated with water heaters are the main reason why the pressure of hot water in the house would be low while that of the cold water is just fine. Why is this though?

To understand why your hot water pressure is low, you first need to understand how your water heater works. The water heater is supplied with cold water using one pipe and hot water leaves the tank on the other side using a different pipe.

Your water heater will either use natural gas to heat the water or electricity. Here is how to troubleshoot a water heater with low hot water pressure:

Check the Shut off Valves

For proper functioning of the water heater, the cold water pipe shut off valve and the hot water pipe shut off valve needs to be fully opened. If any (especially the hot water valve) is not opened all the way, a restriction will be created considerably reducing the hot water pressure.

Check the condition of both of the shut off valve. If the shut off valve is fully opened, the handle needs to be aligned with the water pipe.

In some instances, you might also notice that the hot water copper pipe from the water heater is bent. Bent pipes will without a doubt lower the pressure of the water.

You can either decide to replace the pipe or straighten it if it is in fairly good condition. Use a wrench or channel locks to straighten the pipe.

Never attempted to fix the pipes when hot water is still running through them. You will first need to turn off the cold water supply to the water heater and then drain the heater completely before trying to fix the pipes.

Attempting to straighten the pipe with the hot water still running through it can cause the pipe to loosen or break with hot water gashing out at high pressure. Not only will the water burn you but it will also flood your house.

Remove Sediments/Mineral Deposits from the Exit Pipe Outlet

There is a reason you are advised to drain your water heater at least once every year. Sediments tends to form and settle at the bottom of the water heater which if not drained out has 3 effects:

  • The water heater volumes becomes smaller.
  • Lifetime of the heater is reduced. The sediments eat the body of the heater, making a hole at the bottom. This is the number one reason why water heaters leak from the bottom.
  • The efficiency of the water heater is considerably reduced.

But where does the sediments come from? There are 3 sources for the sediment at the bottom of the water heater:

  • Hard water – Calcium, iron, manganese and other minerals present in the hard water settle at the bottom of the tank.
  • Anode rod – Water heaters are fitted with a sacrificial anode rod. This anode is meant to increase the life of the water heater. Instead of elements in the water corroding the inner lining of the water heater, they instead react and eat away this anode. The compounds formed after the reaction settle at the bottom of the tank.
  • Inner lining of the water heater – If you don’t change your anode rod as is required after every 5 years, the inner lining of the water heated will be corroded and the rust deposited at the bottom of the tank.

If you don’t drain your water heater as frequent as it should be, or if the sediment is being deposited at a very fast rate, your hot water supply pipe exit sediments effectively reducing the hot water pressure in your house.

There are 2 ways you can fix this problem. The first one is to check the status of the hot water pipe exiting the water heater. From experience, that is where the problem usually ease.

Continuous deposition of hard water minerals around the opening forces its diameter to reduce to a point whereby only a trickle of hot water is passing through it. Here is how to fix the problem.

  • Start by turning off the cold water supply to the heater.
  • Turn off the power source to the heater. Always turn off the heater heater source whenever you are draining it to prevent burning the heating element.
  • Put a bucket under the water heater drain valve and slowly open the drain valve with a flathead screwdriver. At this point you don’t need to empty the whole tank. Just a little to prevent water from leaking at the top.
  • Open one of the closest hot water faucet to have air in the system.
  • Use a pipe wrench to loosen the nut connecting the hot water pipe on the water heater.
  • Once loose remove the pipe from the opening. Check for clogs.
  • Most of the time you will find that the opening is badly clogged by mineral deposits. Use a screwdriver to knock of the mineral deposits. If they won’t bulge drill through the clog using a drill with varying bit sizes until the opening is fully unclogged.
  • Connect the pipe back.

Although the above might be enough to fix low hot water pressure in the house, you should go ahead and completely drain and flush the water heater.

How to Drain and Flush a Water Heater

Draining and flushing the water heater allows you remove the sediments from the water heater, and in the process restore the hot water pressure in your house. You can either do this on your own or have a plumber do it for you.

Here is how to drain and flush your water heater:

  • Turn off the pilot light or circuit breaker to the water heater.
  • Close the cold water supply pipe valve.
  • Connect a garden hose pipe on the water heater’s drain valve. Direct its end in a drain somewhere or out in the driveway.
  • To fasten the process, open the nearest hot water faucet. Leave the faucet open until you start refilling the tank. This will prevent having air in the pipes. To prevent sediments from clogging up the faucets aerator, remove it first. The aerator is the attachment at the front of the faucet spout with fine holes. Put a rag around it and loosen it with a wrench to protects its finish.
  • Use a screwdriver to open the drain valve.
  • Let the tank drain completely. Note the color of the water flowing out last from the hose.
  • When there is no more water flowing from the hose, turn on the cold water supply pipe valve to flush the tank. This water will flush out any remaining sediments in the tank.
  • Let the hose drain until only clean water is flowing out.
  • Turn off the drain valve.
  • As the water is filling the tank, you will hear air escaping from the open faucet. Let the air flow out until you have a smooth flow of water. Only then can you turn the faucet off. Clean the aerator and connect it back.
  • When the water heater is full turn on the pilot light or circuit breaker.
  • Check the new hot water pressure in all fixtures.

And basically that is how to flush a water heater and restore hot water pressure in the house.

Related post: The tell-tale signs that need to replace your water heater.

3. Clean or Replace Water Filters

Most homes are fitted with a water filter to catch sediments which prevent them from clogging faucet aerators and showerheads. These filters can either be responsible for the whole house or just one fixture.

The filters often get clogged and in the process considerably reduce the pressure of water flowing through them. Clogged water filters should either be cleaned or replaced.

4. Call a Plumber

If you have tried all the above methods but still the hot water pressure in your house is low compared to the cold water, it is time to call in a professional plumber. Plumbers see these kind of problems day in day out and they know exactly where to look and what to do.

They also have specialized tools and equipment which help them pinpoint where the exact problem is hence they are able to do the job quickly. The only down side to it is the fact that plumbers can be quite expensive.

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