How to Fix Water Heater Low Pressure

According to the Environmental Protection Agency, an average American family uses around 300 or more gallons of water daily. Some of these household chores require the use of hot water. While low water pressure is quite an inconvenience, low hot water pressure could be more exasperating. We discuss the various low hot water pressure scenarios within the home and how to fix the problem.

What causes low hot water pressure?

The hot water pressure in your household should be similar to that of the cold water. If you notice a problem with the hot water pressure, the problem could either be in the water heater itself or the distributing pipes. Some of the most common causes of low hot water pressure are:-

1. A failed or disintegrated dip tube.

In the past, pipes feeding the cold water into the water heaters were located at the bottom thus preventing cold water interfering with the hot water at the top. With time, this model ended in favor of water heaters with both the cold and hot water pipes at the top. To prevent the two from mixing, the cold water inlet is inserted with a tube known as the dip tube. Its purpose is to thrust the cold water at the heater’s bottom where it is heated. The water rises to the top once it’s heated.

The dip tube is made of plastic which, with time, begins to disintegrate. Once they float at the top of the tank, they are bound to get into the water heater’s outlet and travel through the distribution system. They either accumulate in the pipes or fixtures thus causing low hot water pressure.

How to fix a broken dip tube

One of the ways through which you can diagnose that a dip tube is broken is lukewarm water. Should the water from your water heater also appear to have white particles, it could be as a result of a broken dip tube.

Here’s how you can replace it:-

  • When working on any maintenance on your water heater, start off by turning off the power. In the case of an electric water heater, you need to turn it off at the circuit breaker. Gas water heaters normally have the on and off buttons on the tank’s body.
  • Shut off the heater’s supply and drain any hot water by turning on any hot water faucets.
  • Unscrew the supply pipe’s water nipple and gently pull out the dip tube.
  • Lastly, take Teflon tape and wrap it around the threads of the new dip tube. Slip it back into the water heater and reconnect any disassembled parts.
  • Turn on the heater’s cold water supply and turn the power back on.

2. Sediment build-up in the water heater and distribution pipes/ Outdated or corroded pipes due to hot water

With time, sediments, minerals, and rust could collect in the water heater, its outlets, and the pipes. The narrower your distribution system becomes due to being clogged, the more the flow rate of water decreases.

Acidity in the water also eats away at the distribution pipes resulting in leaks. Copper and brass piping are highly susceptible to corrosion which adds on to the clogging and thus reducing water flow. Even where the rest of the piping system is made with corrosion proof material such as PEX but the valves, tees, and elbows are made of either brass or copper, corrosion and the subsequent clogging will still occur.

Corrosion is mostly as a result of the loss of sink in a process referred to as dezincification. This process is more common in hot water pipes.

How to unclog hot water pipes

One of the easiest ways to unclog the water heater pipes is through the use of Rectorseal Calci-Free Tankless Water Heater Flush Kit. This biodegradable descaling solution is meant to restore the efficiency of tankless water heaters by flushing out sediment build-up and limescale in the pipes.

The kit contains

  • 7” feeder hose
  • 7” discharge hose
  • A heavy duty submersible utility pump
  • A pump strainer
  • 2lbs Calci-Free
  • A flush kit bucket

The steps used in the descaling process are as follows:-

  • After turning off the power and shutting off the tank’s supply, proceed to clean the cold water inlet’s screen of any dirt.
  • In the flush kit bucket, mix the Calci-Free with two gallons of water. Mix until the Calci-Free dissolves completely into the water.
  • Position the strainer at the bucket’s bottom and put the pump on the strainer.
  • Connect one end of the hose to the discharge connection on the pump while the other end goes to cold isolation valve.
  • Connect one end of the second hose to the hot isolation valve and place the other end into the bucket containing the Calci-Free solution, and open the cold and hot isolation valves.
  • Turn the pump on and let the Calci-Free solution for at least 20-30 minutes after which you should clean up your unit according to the manufacturer’s instructions.
  • Turn off the pump and close the cold isolation valve. Remove the connected hose and get rid of the used solution according to the local laws.
  • Open the water supply and allow the water to circulate for around 5 minutes while draining into the bucket. Empty the bucket and close the hot water isolation valve.
  • Reconnect the power source.

Water heater manufacturers recommend that you do this at least twice every year.

3. A dusty or failed filter

The water filter is a mesh at the bottom of your water heating unit whose purpose is to capture sediments and mineral particles before they get into your home’s hot water supply system.

Eventually, dirt and grime build up on the air filter reducing the flow of air to your system. The result is a highly inefficient system with one of the problems being low pressure. You can clean the filter yourself as it is an easy and straightforward process.

How to clean the filter

  • After turning off the power and cold water supply, locate the filter’s catch mechanism, undo it and remove the heater’s bottom.
  • You can use compressed air to blow the dust off the filter. In the absence of an air compressor, lay down the filter on the ground and use a hose to spray it with water until all the dirt is removed.
  • If you’ve used water to clean it, you will need to hang it to dry or wipe it with an absorbent cloth.
  • Reinstall the clean filter and use the catch mechanism to secure it in place.

Consider cleaning the water heater’s filter every time you flush it.

Another way of protecting your filter and more so the entire system is by installing a hot water system protector such as Aqua-Pure AP430SS Hot Water System Protector. Its purpose is to prevent scale build-up and is normally installed on the pipe leading to the system. It has polyphosphates which inhibit scaling in the filter and the water heating unit by binding magnesium and calcium minerals and prevents them from precipitating on the metal surfaces such as the hot water faucets, shower heads, and more importantly the filter.

How to install Aqua-Pure AP430SS Hot Water System Protector

For this project you will need PTFE tape, one ¾” stop and waste compression valve, two male ¾” adaptor and ¾” street adapter, a pipe cutter, and a ¾” compression gate valve. Follow the following process or alternatively, have a professional plumber install the equipment.

  • Use the PTFE tape to wrap the adapters’ threaded ends and screw them into the cartridge head.
  • Fit the compression fittings loosely onto the head of the cartridge with adapters and mark the length of the pipe that’s likely to be removed.
  • Use the pipe cutter to cut off this part.
  • Use the valve compression fitting to fasten the stop and waste valve to the water heater. Ascertain that the indicator arrow points towards the AP430SS unit so that the drain nut is easily accessible for pressure release when you are changing the system’s cartridge. Tighten the drain valve’s nut.
  • Use the valve compression fitting to link the gate valve with the system’s water supply pipe. Tighten the compression nut. Keep the unit’s head assembly vertical.
  • Once done, turn on the water and power supply and ensure there are no leaks.

4. A rusty or damaged hot water valve

With time, the valves on your unit get dirty, rusty, and corroded. This leads to leaks and, therefore, low water pressure.

Damaged water valves can also affect the flow of water into and out of the water heater unit. As well, valves turn. This implies that they could be turned off or moved accidentally. This will affect the flow into and out of the water heater.

How to clean or replace dirty valves

  • Turn off the cold water supply and drain the unit by attaching a garden hose on the unit’s drain valve. Open a hot water faucet and drain all the hot water in the system.
  • Use a screwdriver to remove the panels that could be limiting your access to the valves
  • Remove the valves and clean them with a solution of water and vinegar or sodium carbonate and water. The solution should have 2 tablespoons of either sodium carbonate or vinegar and a quart of hot water. You can use a scouring pad to scrub off the dirt.
  • Replace the valves once they are clean and open the water supply. Turn on the power and remember to check for leaks.

If the valves are too corroded, consider replacing them with the Watts LFTWH-FT-HCN Service Valve Kit for Tankless Water Heater. This is a valve kit that has numerous valves that are designed to ease the installation, maintenance, as well as the heater’s operation.

With the Watts LFTWH-FT-HCN Service Valve Kit, 18 water heater fittings can be replaced as well as 16 connectors normally used in tankless water heater models.

5. Your water supplier

Low hot water pressure could also be as a result of low water pressure from your water supplier. If you have done all the above and the hot water pressure issue still persists, it could be a problem from the supplier. You can diagnose a low water pressure issue using an inexpensive pressure gauge obtained from any home improvement or hardware store. A good example is the Milton 1195 ¼” NPT High-Pressure Gauge.

Shut off all water faucets, showerheads, and appliances that are using water. Hook the gauge to the pipe supplying your household. Tighten the gauge and open the shutoff valve.

The pressure gauge will give you a reading of your water’s pressure. If it is between 45 to 55 psi it is alright. A reading that is below 40 psi is indicative of low water pressure and you should consider installing a pressure booster such as Simer 3075SS-01 ¾ HP Pressure Booster Pump.

How to install a pressure booster

Before commencing, check on the local plumbing laws to ensure that you are compliant. Some jurisdictions dictate that the work is done by a professional. If not, follow the below steps.

  • After turning off the main water valve, use a tube cutter to cut the supply pipe.
  • Place the pressure booster and connect it with the fittings and copper pipes to the supply pipe.
  • Solder the parts together and call an electrician to connect the booster pump to the electric panel.
  • Once they are done, open the water valve and switch on the pump. Measure the new pressure.

Low hot water pressure in the whole house

In this case, the problem could be with the water heater itself. The first thing you should check is the shut-off valve leading into the heater to ascertain that it is not partially closed. If it is not, check on the inlet and outlet pressure. The outlet’s pressure only matches the inlet’s pressure. You can diagnose the pressure by fixing a garden hose at the bottom of the water heater. A good flow implies that the problem is with your distribution system and not your heater. If the flow is weak, the verdict could be sediment build-up or low pressure on the inlet or a failed outlet valve.

Sudden loss of hot water pressure

If the hot water pressure suddenly goes down while the cold water pressure flows just fine, an internal valve within the water heater may have failed. Sediments may have traveled into the system and blocked a valve or pipe. A sudden drop in hot water pressure is illusory. Rather, it indicates an inhibited flow.

Low hot water pressure in a specific place

1. Low hot water pressure in the shower and bathtub

Should the low hot water pressure be limited to your bathtub faucet or showerhead, you need to remove both and clean the aerators. Shut off the supply to the whole house before commencing. You can pry out the showerhead with pliers and clean it exhaustively.

If the low hot water pressure is only at the bathtub, you will need to adjust the temperature limiter on top of cleaning the faucet.  Locate the screws on either side of the faucet to locate the limiter which should be connected to the faucet’s stem. Rotate it to the left to increase hot water output. If there’s no limiter, disassemble the faucet as you would any other and clean it appropriately.

Once you’re done, reassemble the showerhead or faucet and check on the pressure. If the problem persists, you might need to replace them.

2. Low hot water pressure in the kitchen

Check that the shut-off valve under the sink is not partially open. If you open it all the way and there is no difference with the flow, shut it off and detach the supply pipe from the faucet. Point the pipe into a bucket and turn the valve on. If the flow is still low, the problem could be with the valve or the supply pipe.

If the flow from the supply pipe is fine, disassemble the faucet and clean it. Alternatively, you could replace it.

3. Low water pressure after replacing the water heater

Most people have a low-pressure problem after installing a new water heater. As the system is still new, we can rule out scaling or sediment buildup. It is possible that the water heater valves are not turned all the way after installation, so, that makes it the first thing you should check.

Ever heard of the whistling or humming sound produced by new water heaters? New water heaters are usually installed with heat traps whose aim is to improve energy efficiency. They produce the sound when they restrict flow, which could also result in low water pressure. Replacing the heat traps with dielectric nipples will remedy the situation.

Final thoughts

With proper maintenance, you can avoid problems that could bring about low hot water pressure problems. Maintenance also lengthens your system’s lifespan and causes it to be more energy efficient. No matter how well you maintain and clean your unit, problems still do occur. We hope that the above guide has covered most of your problems about How to Fix Water Heater Low Pressure. Should you have any other suggestions, feel free to share them on the comments.


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