Here's the situation:

  • Almost no hot water pressure (just a trickle) at all outputs (not just a single sink with an issue)
  • Cold water runs fine and has full pressure
  • Water heater is tank-style and is not leaking
  • Water heater was not regularly drained to reduce sediment buildup (and is old enough to likely have plenty of sediment inside)

Here's my rather uneducated guess: that sediment has built up inside the water heater and is clogging the exit pipe.

A repairman from the natural gas company inspected the water heater and said it's an easy repair: all that needs to be done is to clean off the water heater's exit pipe filter screen.

Okay... so I've searched all over the interwebs and I have not found a single site or video showing how to do this, or even if such a filter actually exists.

Is my guess of the cause of the issue a reasonable guess? Is the repairman's recommendation correct? Either way, besides calling a plumber, what's the best way to restore the hot water pressure?

  • Have you turned the shut-off valves recently for some reason? Valve failure is a way more likely cause of this. Aug 3, 2016 at 4:32
  • @JimmyFix-it Thanks for your question, Jimmy. No one has touched them at all. Aug 3, 2016 at 4:54
  • I had this same problem … and it was caused by the filter screen in the hot water exit pipe just above the ta Feb 11, 2020 at 14:52
  • @KevinMahoney Thanks Kevin. Your comment got cut off. Can you edit or re-post it? Feb 12, 2020 at 10:24

2 Answers 2


It is fairly unlikely for boiler deposits/sediment to have blocked the outlet pipe as it is at the top of the tank, it is large, and sediment (by definition) settles to the bottom. I have never seen an "exit pipe filter screen".

A common problem is old shut-off valves not opening back up completely after they have been exercised. Another problem I have seen are these gimmick "heat-trapping" nipples installed at the heater inlet, they have little ball-check valves that fail and restrict water flow.

I live in an area with hard water (lots of minerals/dissolved solids) and I have never backflushed my water heater; it has been in service for 16 years with no problems. I am not saying you should not do it, I am just saying that the value is overrated when it comes to longevity (efficiency is another story).

  • I have never seen it either (although I am not very experienced with this), but here is a video showing it happening: youtube.com/watch?v=koD7-FSxIBc . Since I have not exercised the shut-off valves, hopefully that's not an issue. But those "heat-trapping" nipples are something that I don't know anything about (oh, the possibility for so many jokes). How would those be diagnosed or repaired? Perhaps you can add that to your answer. Either way, a thumbs up for your ideas and assistance! Aug 3, 2016 at 4:59
  • I agree with Jimmy Fix-it. Sediment will not cause this problem. I also suspect a valve problem. Exercise the valves, see if that helps. BTW, flushing water heaters is important to help control bacteria that loves to grow in water under 135 degrees F. Never, ever use water from the heater for drinking or cooking. Make you sick to see the stuff I have flushed out of water heaters. Aug 3, 2016 at 11:38

I had this same problem, and it was caused by a clogged filter screen in the hot water exit pipe just above the tank. Over the course of several months, I noticed my hot water pressure throughout the house had decreased. It was usable, but clearly less pressure than the cold water output. I thought there may be air in the tank or pipes so I decided to drain the tank (3-year old AO Smith 50-gallons). I followed the recommended maintenance steps and a good amount of sediment drained. Unfortunately, there must have still be some in the tank when I decided to refill it.

Upon refilling the tank, virtually no water came from the hot water faucets. There was minor water in the slop sink in the basement but nothing on the second floor. My plumber inspected the hot water pipe at the top of the tank and found a fully clogged filter screen. It must have been filling over time which is why I noticed pressure decreasing recently and turning on the faucets after refilling the tank was the final straw. He told me that the filter was not necessary and reconnected the pipe. After blowing out some air, the hot water output at each outlet was better than I could recall.

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    Hello, and welcome to Home Improvement. Thanks for the answer; keep 'em coming. And, you should probably take our tour so you'll know how best to contribute here. Feb 13, 2020 at 14:26

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