Why your hot water pressure drops and what you can do about it

Low hot water pressure usually comes from one of three places: mineral buildup in the showerhead or faucet aerator, a partially closed valve on the hot water line, or sediment inside your water heater. The good news is that most of these are things you can fix yourself in under an hour, and none of them require a plumber's visit unless something is actually broken.

Cold water pressure stays normal while hot water pressure falls because the hot side of your plumbing system is more vulnerable to blockages. Minerals from your water settle out as the water heats, and they stick to the inside of pipes, valves, and fixtures. If only your hot water is weak, the problem is on the hot side. If both hot and cold are weak, the issue is earlier in your line — usually a main valve or the meter.

Key Takeaways

  • Clean the aerator (the screen at the tip of your faucet) by unscrewing it, rinsing it under running water, and soaking it in white vinegar for 30 minutes to dissolve mineral deposits.
  • Check the shut-off valve under your sink or near your water heater — it should be fully open (handle parallel to the pipe), not partially closed.
  • Flush your water heater by attaching a garden hose to the drain valve at the bottom and letting water run until it runs clear, which removes sediment that blocks flow.
  • If pressure is weak everywhere in your house, check the main shut-off valve where the water line enters your home — it may have been left partially closed after repairs.

Clean the aerator and showerhead first

The aerator is the small screen at the end of your faucet. Mineral deposits clog it faster than anywhere else because water slows down there and minerals have time to settle. Unscrew it by hand — most turn counterclockwise — and hold it under running water. If water still trickles through, soak it in white vinegar for 30 minutes, then scrub the screen with an old toothbrush and rinse it again.

For showerheads, the same method works. If the showerhead is fixed to the wall, you may need a wrench to unscrew it. Soak it in a plastic bag filled with white vinegar — you can hang the bag around the showerhead with a rubber band so you do not have to remove it. After 30 minutes, run hot water through it and scrub any remaining deposits with a toothbrush.

This step alone fixes the problem in most cases where only one fixture has low pressure. If pressure improves but is still not what it was, the problem is also inside your pipes or water heater.

Check the shut-off valves under your sink and at your water heater

Under your sink, you will find two shut-off valves — one for hot water and one for cold. They look like small knobs or levers attached to the pipes. The handle should be parallel to the pipe (pointing the same direction the water flows). If the hot water valve handle is perpendicular to the pipe (pointing across it), the valve is closed or partially closed. Turn it until it is parallel to the pipe.

Do the same check at your water heater. There is a shut-off valve on the cold water line coming in at the top. If someone did plumbing work recently, this valve may have been left partially closed. Turn it fully open.

If you turn a valve and nothing changes, it was already open. If pressure jumps back to normal, you have found the problem.

Flush sediment from your water heater

Over time, minerals in your water settle to the bottom of your water heater tank as sediment. This buildup reduces the space for hot water and can block the outlet pipe, lowering pressure throughout your house. Flushing the tank removes this sediment and usually restores pressure.

Turn off the power to your water heater (switch off the breaker for electric, or turn the gas knob to "pilot" for gas). Wait 30 minutes for the water to cool slightly. Attach a garden hose to the drain valve at the bottom of the tank — it looks like a faucet handle near the floor. Put the other end of the hose in a floor drain, sink, or outside where water can run safely.

Open the drain valve slowly. Water will flow out. Let it run until the water runs clear instead of brown or cloudy — this usually takes 10 to 20 minutes. Close the valve, disconnect the hose, and turn the power back on. Check your hot water pressure at a sink or shower.

If you are not comfortable doing this, a plumber can flush the tank for you, usually for $150 to $300. Do not skip this step if sediment is the problem — pressure will not improve otherwise.

Check the main shut-off valve if pressure is low everywhere

If both hot and cold water pressure are weak throughout your house, the problem is not on the hot side — it is earlier. Find your main shut-off valve where the water line enters your home. It is usually in the basement, crawl space, or near the front of the house where the meter is. The valve handle should be parallel to the pipe.

If the handle is perpendicular, turn it parallel to open the valve fully. If it is already parallel and pressure is still low, the problem may be at the meter or the city's main line — call your water company to check.

When to call a plumber

If you have cleaned the aerators, checked all the valves, and flushed the water heater and pressure is still low, something inside your pipes is blocked. This could be corrosion in old galvanized pipes, mineral buildup deep in the line, or a broken valve that looks open but is not. A plumber can pressure-test your line to find where the blockage is.

If your water heater is more than 10 years old and flushing did not help, the tank may be failing internally. A plumber can inspect it and tell you whether it can be repaired or needs to be replaced.

Frequently Asked Questions

Why is my hot water pressure low but cold water pressure is normal?

The hot water side of your plumbing is more prone to mineral buildup because minerals settle out as water heats. Check the aerator first, then the shut-off valve under your sink, then flush your water heater. If only one fixture is affected, the aerator is usually the culprit.

Can I flush my water heater myself or do I need a plumber?

You can flush it yourself if you are comfortable with basic plumbing. The process takes about 30 minutes and requires only a garden hose and a wrench. If you are unsure, a plumber can do it for $150 to $300. Do not skip flushing if sediment is the problem — it will not resolve on its own.

How often should I clean my aerator?

Clean it once a year if you have hard water, or whenever you notice pressure dropping at a single faucet. It takes five minutes and costs nothing. If you notice it clogging more than twice a year, consider installing a whole-house water softener to reduce mineral buildup throughout your system.

What if I turn the shut-off valve and it will not move?

Do not force it — you may break it. If a valve is stuck, it has likely not been opened in years. Spray it with penetrating oil, wait 15 minutes, and try again gently. If it still will not budge, call a plumber. A stuck valve usually means it needs to be replaced anyway.

Is low hot water pressure a sign my water heater is failing?

Not always. Most of the time it is sediment buildup, which flushing fixes. If your water heater is more than 10 years old, flushing did not help, and you see rust stains around the base, the tank may be failing. A plumber can inspect it and tell you whether repair or replacement is needed.