Plumbing in the Home/Water heater noise


I have a gas water heater (50 gal) that is 5 year old and that supplies hot water to our bathrooms (kitchen, washer, etc., are on a different water heater).  About 3 weeks ago, it started making a banging noise.  The noise occurs after we take showers, usually in the evening.  It's a single "bang" that occurs once every 30-60 seconds or so, maybe longer.  It's loud enough to hear it upstairs, on the ground floor in the room directly above the heater.  It lasts for about an hour.  I tried flushing the heater twice.  Both times, the water came out clear and the problem was not fixed.  Then, I thought that it was the expansion tank and I replaced it but the problem was not fixed.  When I flip the lever of the safety valve, water comes out as it should.  The sound seems to be coming from the top part of the heater.  We live in PA and recently we have had very cold weather and the water is very cold too.  Also, I never measured our water pressure but it seems a bit higher that other homes where I have lived.  We do have hard water. It's a 50 year old single house.  I have been flushing the heater once in a while but not as often as I should (it has been flushed 3-4 times in the past 5 years, not counting the two times when I did it recently and every time the water that came out was clear).  Is there anything else that I can try before calling a pro?  Could the cause be sediment even though the water coming out was always clear?  What else could cause such a banging noise?

It sounds like you have a combination of things going on. In the past 5 or 10 years or so the heater manufacturers have been sending them out with a simple check valve system built into the pipe nipples that screw directly into the top of the heater. as they age the checks can stick and when the water is turned on the pop and cause a noise. Also, hard water make the situation a bit worse due to deposits. It's nothing serious, just annoying. Repiping the inlet and out .and removing the nipples will probably stop the noise  As for flushing the tank, don't waste you time . The tank is con vexed at the bottom and sediment gets trapped. Running water out the bottom drain doesn't do the job.  I would  probably not worry about it since the new tanks only last 8 to ten years.  

Plumbing in the Home

All Answers

Answers by Expert:

Ask Experts


Jay Nicholas


Plumbing & Heating (warm air, hot water & steam heat)


40 years in the business, 35 years as a lic. master plumber in NY State. Retired

Graduated Magna cum laude at the School of Hard Knocks

Past/Present Clients
Commercial, residential and light industrial. You name it ...I have probably worked on it

©2016 All rights reserved.