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Hello everyone,
We just had a new Hotpoint 40 gallon, gas, direct vent
water heater installed.When the cold water is shut off anywhere in the
house, by us or an appliance, a loud metallic bang can be
heard coming from the water heater, followed
by three or four additional knocks which get softer until they
stop. It sounds like something is swinging inside
the water heater and hitting something over and
over again.No noise is heard when the hot water, or a mixture
of hot and cold water is shut off. Only straight cold water.Could the drip tube be smashing into something, or do you have
any other ideas?Thanks for the help!
» This message has been edited by UTahJ on 28 January 2004
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Most likely one of two things,
First and most common is a valve that is not completely closing. Turn the water off to the clotheswasher and see if it goes away, then turn the water of to the toilets and see if it changes. If this does not isolate it the next most common possibility is that you have a closed domestic water system. Being that there is either a backflow preventor or pressure regulator on the incoming line. As water heats up in the tank it expands and pressure buildsup because it can not desipate into the water supply system because it is closed. The excess pressure will make all sorts of noise when valves are operated. Most likely the first scenario will fit. Let us know! -
Thank you for the reply.
I tried turning off the supply to the washing machine,
and the toilet separately, and then I tried them together.
(we don’t have anything else that would use cold water
other than the kitchen and bathroom faucets), but the
banging in the water heater persisted.
It appears to be a closed loop system as you stated,
however there isn’t a pressure regulator or backflow
preventor visible inside the house. The line exits
through the basement floor and runs about 20 feet
to the city shut off valve in the front yard. And the rest
of the system is just plain old copper pipe.The noise wasn’t present with the old water heater
we had, but that thing wasn’t very efficient either, so
maybe thermal expansion wasn’t an issue.Any other suggestion?
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Fairly certain that your problem is related to a loose fitting pipe on your water line somewhere that is not properly clipped or strapped.
Simply, when you close a tap under mains pressure the shock wave causes a vibration we call water hammer within pipes on ocassions. This is usually more commonplace with appliances that have fast opening or closing solenoid valve that “slam” shut causing the shock wave in the piping system. If you cannot locate the loose pipe you can fit a device into the water line called a water hammer arrestor that will do the job for you.
You should also check and make sure that the water heater has a pressure limiting valve fitted on the inlet cold water line to it – the purpose of this device is to ensure that water pressure does not exceed that to which the water heater relief valve has been set, thereby no stressing any other valves within the system.
Selgas Services Ltd
Craftsman Gasfitters, Plumbers, Electrical Service Technicians -
Thanks for the reply Peter.
The noise is definitely coming from inside the
water heater. I don’t hear any noises from the
rest of the piping in the system.I tried putting the smaller, bladder type, water
hammer arrestors on the toilet, kitchen sink,
and the washing machine cold water lines this evening,
but they didn’t do a darn thing. Maybe I should
have tried them on the hot water side, but I got
discouraged by the inital results on the cold side.You’re idea about a pressure limiting valve on
the hot water inlet might be my only choice.
My only concern is that I played around with adjusting
the cold water inlet valve on the water heater, to
see if I could eliminate the bang. The only time
it disappeared was when the cold water was almost
all the way off, thereby reducing our hot water pressure.I’ll check into the value though… I’m sure what ever
is making the noise in the water heater is bound to
break eventually… not a good thing.Thanks again!
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http://www.wattscanada.com/faq/regulators/main.html
http://www.wattsreg.com <<<< click on products, then thermal expansion..........this is a recommended item on a closed system.
Once you know your water pressure, then make the decision to go with the PRV………which should be on the main water line immediately following the main shut off valve to protect the entire plumbing system, hot and cold.» This message has been edited by DUNBAR on 29 January 2004
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turdchaser:
I liked your idea, so I tried it as soon as I got
home. I shut off the water heater and ran the hot
water until it ran cold. Guess what… same noise.
I guess that rules out thermal expansion problems.So I’m assuming I have water pressure that’s high
enough to make something in my hot water heater rattle
around when a faucet is turned off.Two more questions before I call the plumber back:
1. If I had to turn the cold water supply to the water
heater almost all the way off before the bang stopped,
wouldn’t I have to set the pressure reducing valve
to such a low PSI that it would be unbearable, just
to acheive the same effect?2. What are the odds that the water heater we purchased
is just faulty, with something loose inside?Thanks for everyone’s help!
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Yes, exactly. We have eliminated thermal expansion as well as the noise that air escaping from the water in a gas water heater makes as it heats up. The likelyhood of the tank being faulty and causing it is low. It is possible but very unlikely. Personnally I have had guys drop tanks and there be visible damage to the outside. I have turned around and sold them at a loss and personnally backed up the warranty and have yet Had a problem with one. This is why I say it is possible but unlikely. Have the plumber inspect the water supply piping for any causes and if none are found the following product is your best bet to fixing the problem. It should be installed on the cold water supply just before the tank. http://www.amtrol.com/website/content.nsf
click on homeowner general info., click products red button, click residential, expansion tanks then therm-X-Trol
Do let us know how it turns out when you get it fixed.» This message has been edited by turdchaser on 30 January 2004
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Ahhhhhh ha from your last post I would not be surprised to find the fault being a broken off or very loose hanging anode rod or dipper tube in the cylinder itself – if these were at fault then the noise would only be evident when hot water was being run or when a hot tap was turned off.
These problems on a new cylinder would indicate to me that it had been mistreated when being transported. Both of these components can be easily changed or checked as they either screw into the cylinder or fit inside one of the water connections.
The problem you have explained is less likely to to be pressure related but more something amiss within the tank itself.
Selgas Services Ltd
Craftsman Gasfitters, Plumbers, Electrical Service Technicians -
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All dip tubes are plastic now. The anode rod is a stiff approx 1/8th in. rod that hangs down from the nut it is secured to. The only other thing inside a gas tank is the the combination gas, thermostat valve which screws into the side of the tank. If you wish to remove the anode simply depressurize the hot water and drain a little water out of the tank and unscrew it, cut it off of the nut and screw the nut back into the hole. By removing it you will decrease the life of the tank.
» This message has been edited by turdchaser on 31 January 2004
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turdchaser:
Thanks for the info. I think I’ll run down to the hardware store to see if they have a “bolt” that
will act as a temporary plug after I pull the rod out. I don’t want to destroy the rod, I just want to eliminate
it as a possible cause of the noise.I suppose a replacement rod would have to be
ordered through Hotpoint, eh? -
http://www.waterheaterrescue.com/pages/WHRpages/English/water-heater-anodes.html
That is what an anode rod looks like.
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I suspect that you have excessive pressure from your house water main, and that there is probably nothing wrong with your water heater. You probably tee’d off your house cold water lines from your WH cold inlet, and when a cold fixture valve shuts you are getting water hammer transmitted back to your WH. You should ahve a pressure limiting valve at the entrance of the supply line to your house. If not, intall one. As regards water hammer, you can install water hammer arrestors at each fixture, or better yet, install a multitube arrestor on the supply line where it enters the house. And, of course, make sure that all of your pipes are securely held to the structural members of your house.
Finally, you could install an expansion tank atop your WH, but this helps only if your noise is due to hot water expansion, which you state you have ruled out.
NtP
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http://www.users.bigpond.net.au/bungie/hammer/
DISCLAIMERAll advice is given with-out seeing the job, and hence all advice MUST be taken as advice with limited knowledge on the exact situation. NO responsibility can or will be taken. And yes, I am a licensed Plumber and Drainer with my own business in Brisbane Australia.
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