Installed new gas DHW. Getting random pipe banging on hot pipes only. No water running for a while, then random banging. Expansion tank installed. City water @ 65 psi. CPVC plumbing. Normal house. Nothing out of ordinary in house. ??????????
Random hot only pipes banging. No water running.
- Thread starter Hoeburd
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Thank you. All correct. The noise is an air hammer noises but no water is running/stopping causing sound. My guess is expansion but an expansion tank is installed on cold side. I would think this would accept the expansion. Not to mention the expansion should dissipate in the main. Expansion tank is not required by code here. Water softener is installed and working. So, minerals is out as reason. I can't see how air gets Into closed system in city water/sewer. Water heater a month old so no sedimate in tank. Think it could be a heat trap issue? Maybe damaged from factory or during instsll not allowing pressure out of hot side?
wpns
Well-Known Member
It’s your pipes that are expanding in the walls, hanging up, and then suddenly releasing. Is the temperature higher than it was before?
Definitely not hanging up. I hear hangers very slightly "ticking" when hot water is on slightly expanding the plastic hangers. I've tried greatly lowering temp for a few days to see if it was temp... Same result. It seems like the pressure in hot can't relieve itself. And again, expansion tank is new and on cold inlet about 12" above tank. Could a sink or shower valve be back feeding??? I'm running out of ideas haha. I've had a plumber out. That's when expansion tank was installed about a week after WH install. I was trying to figure out myself b4 plumber charges me to experiment.
wpns
Well-Known Member
Sounds like there's a check valve between the expansion tank and the hot water heater, maybe built into the hot water heater or something? Can you put a pressure gauge on the hot water side (maybe the tank drain or a clothes washer hookup?) to see if you are getting high pressure?
It definitely seems like a check would be between the tank and expansion tank. But, I don't think an actual check is in place. Heat traps are in the tank nipples where the copper connect to the tank. But, from what I read, heat traps are not check valves. Not sure if 1 can get hung up?? I have a pressure gauge. I've hooked up to cold side and get 65psi static. Embarrassed I've not thought to try hot side. I can connect to tank drain when it's making the noise to see if pressure is high or surges!! I'll keep you posted with results!
wpns
Well-Known Member
Also, if it's banging, are you getting any water out the overtemp/overpressure relief valve? If there is pressure being released somewhere, then there's water coming out somewhere...
No water out of pressure relief valve. Incoming pressure between 60-70 pounds. PRV prob have a rating of lime 120 pounds or something. But, it pressure in hot side is higher than cold side and it can't escape I would hear bang. In theory, pressure on hot and cold side should be about same.
Do you have a pressure reducing valve in your system ?
Could it be the water heater itself making noise ? Like the vent pipe or burn chamber ?
Could it be the water heater itself making noise ? Like the vent pipe or burn chamber ?
I don't have a PRV. City pressure is 65 pounds. I don't think it's the heater. I can feel the pipe shake each time it bangs.
So this is happening 24/7 ? Hot water recirculating system ?
Completely random. It's actually doing it right now. And kids just showered about 30 min ago. So now, not 100% sure it's an expansion issue because the pressure was just relieved in hot side...
Thermal expansion happens when the system is closed and the water heater is heating. So it’s prime time right after the water is cut off from a shower.
But you say that you’ve connected a gauge and the pressure wasn’t high while the noise is occurring.
Are you sure it’s even plumbing related ?
While the noise is happening I suggest walking to the water heater and see if the water heater itself is causing the noise.
But you say that you’ve connected a gauge and the pressure wasn’t high while the noise is occurring.
Are you sure it’s even plumbing related ?
While the noise is happening I suggest walking to the water heater and see if the water heater itself is causing the noise.
The hot pipes are banging and moving. Definitely plumbing related somehow. Cold city supply is 65 pounds. Guage on drain of water heater now. Reading maybe 67 pounds. I lived here 2 years. Didn't make a sound for 1.5 years. Got new water heater. Bang... but that could just be weird coincidence. It was banging when kids were physically in shower. If I turn on dishwasher when it's banging, it will stop. But... how would a dishwasher cause banging? Haha. Could just be the water filling dishwasher releasing pressure. But, y not when shower running. Super annoying and weird. Just didn't wanna have plumber charge $90 dispatched fee then obviously not know exactly what it is and cost me $1000 to TRY to figure out. But, it might have come to that
You’ve said it bangs when no water is being used.
You’ve said it bangs whenever water is being used and it stops if you turn on the dishwasher.
You didn’t answer when I asked if you have a hot water recirculating system.
To check for thermal expansion, with the gauge connected, run some hot water until your water heater fires off. Then shut the water off at the hot faucet and do not allow any water to be used anywhere…….now, watch the gauge as your water heater is heating and check to see if pressure rises.
If any water is used or leaks anywhere in the system the test will be invalid.
Very few things can cause your issue.
The fact that it’s happening with no water being used is key….it points toward thermal expansion or a pressure reducing valve.
You’ve said you don’t have either…..
I think you’re giving bad info. Not on purpose, but bad info ultimately.
Any water treatment system installed ?
Trap primer ?
Automatic valves of any type ?
With the noise happening, go to your water meter and listen. See if the sound is originating at the water meter. Use a piece of pipe to touch the meter with the other end to your ear. Listen…..
You’ve said it bangs whenever water is being used and it stops if you turn on the dishwasher.
You didn’t answer when I asked if you have a hot water recirculating system.
To check for thermal expansion, with the gauge connected, run some hot water until your water heater fires off. Then shut the water off at the hot faucet and do not allow any water to be used anywhere…….now, watch the gauge as your water heater is heating and check to see if pressure rises.
If any water is used or leaks anywhere in the system the test will be invalid.
Very few things can cause your issue.
The fact that it’s happening with no water being used is key….it points toward thermal expansion or a pressure reducing valve.
You’ve said you don’t have either…..
I think you’re giving bad info. Not on purpose, but bad info ultimately.
Any water treatment system installed ?
Trap primer ?
Automatic valves of any type ?
With the noise happening, go to your water meter and listen. See if the sound is originating at the water meter. Use a piece of pipe to touch the meter with the other end to your ear. Listen…..
With no check valve at the water meter, water can flow through the meter and flow backwards through the meter.
No water has to be used for water to flow backwards and forwards through the meter. Varying street pressure can cause this.
That could possibly be a source of noise.
No water has to be used for water to flow backwards and forwards through the meter. Varying street pressure can cause this.
That could possibly be a source of noise.
No re-circulation system. I do have a softener. No PRV installed. No automatic valves. I do have an expansion tank on cold side entering hot water heater.
New development... I was hearing noise last night when everything was idel. No water running. Since running dishwasher seems to stop noise, I valved off makeup line to dishwasher when it was banging. After valving off, I didn't hear noise any longer. After about 3 hours of quiet, I heard a very slight "ticking" from dishwasher. And... dishwasher was off when this was occuring. I opened the makeup valve and instantly heard the banging again. So, maybe the stupid dishwasher has something to do with it. No idea how and maybe not problem but I will need to Investigate further. I believe dishwasher fill valves are solenoid valves which open and close almost instantly. That could cause hammer but the dishwasher is off when noise is occuring... sooooo. Beats me.
I mean, with Guage on cold side the static city pressure is consistent. I have "fancy" digital water meter so no small water wheel that spins when water travels through. So other than listening, I can't tell when water is flowing through meter. I'll see kf I hear water flowing when everything is off.
wpns
Well-Known Member
Sounds like the dishwasher is popping it’s solenoid valve open when the pressure gets high enough. Maybe your water softener has a checkvalve?
How is the hot water pressure as measured at the bottom of the tank?
How is the hot water pressure as measured at the bottom of the tank?
I have to do more investigating but that is what it sounds like. I just don't know why it would be doing it with the dishwasher off. But I don't know enough about the appliance 2 know if that's normal. Pressure at bottom of tank is from a Guage I have threaded onto drain. Maybe just something faulty in dishwasher.