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5 Reasons Your Tankless Water Heater Is Losing Water Pressure

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Tankless water heaters can suffer from low pressure output when an undersized model is installed in a home, but sometimes a pressure drop only occurs after the heater has been successfully used for years. Don't ditch your heater just because its performance is changing. Find out what's wrong by troubleshooting for these five common causes of tankless water heater pressure loss.

Clogged Inlet Screen

Some installers add an extra part that fits between the inlet hose for cold water and the heater. Commonly called the inlet screen or filter, this is a straight or T-shaped piece of PVC or metal pipe. It threads or clamps onto the inlet hose, depending on the design of your tankless unit and the type of pipe or hose installed in your home.

Unscrew or unclamp this part and check the mesh inside. Hard water causes minerals to build up and clog the filter, which also happens in sink aerators and shower heads. Other sediment like fine sand can also create clogs. You can soak the screen in vinegar to attempt to dissolve the minerals, but the part is inexpensive and easy to replace too.

Increased Water Demand

How have your family's habits changed over the months and years of use since you first installed the water heater? Many people don't realize that they're taking the instant hot water for granted and forgot about the water limit on even the best tankless model. Each concurrent use of a faucet or appliance elsewhere in the house lowers the water pressure while you're taking a shower at the same time.

It's very easy to see if this is the cause of your issue -- simply make sure no one else is using any water and see how the pressure is at each tap. If this is your problem, try

  • Setting up a written schedule so the family knows when to wash dishes and take showers
  • Installing more tankless heaters in different rooms to expand capacity
  • Switching to appliances, like dishwashers and washing machines, with built-in water heating units.

Plugged Water Coil

Instead of using a tank that circulates dozens of gallons around a heating element, the tankless heater runs water through a twisted coil right over the element to get the temperature up faster. The same well water sediment and dissolved minerals can create serious clogs in this coil, and you won't be able to tell if this is what's blocking your water pressure until you rule out all the other causes. Don't try to open the unit and inspect the coil yourself. A professional can quickly determine if it's clogged and either clean it with acid or simply replace it.

Temperature Setting

Has anyone in the family recently changed the water temperature dial on the tankless heater? Turning up the heat setting causes the water to flow out more slowly because the unit has to hold back more of the flow to keep it exposed a little longer to the element. Turning down the temperature at the heater and using a hotter mix at the tap could give you an immediate small boost in water pressure.

Upstream Problem

Finally, don't forget that other parts of your hot water system can mess with your water pressure before it reaches the heater. Even if the cold water tap is still flowing strongly, the inlet hose or pipe leading to the heater can become clogged by minerals too if it's a galvanized pipe. Water softeners are also prone to reducing pressure, but they tend to affect both temperatures of water evenly. Have your pipes inspected for other issues when a plumber from a company like First Class Plumbing of Florida Inc. rules out any potential problems with the tankless water heater itself.


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