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Water hammer really loud?

remagenman

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Oct 30, 2011
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439
Excuse my ignorance to plumbing but I think the very loud house shaking noise that occasionally bangs underneath my house is the water hammer?

Nothing will be on and as I am walking across the room a loud rumble in my crawlspace, I assume, happens from time to time.
 
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remagenman

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Are you on a well or city water.

If it’s a well it maybe the pump kicking on and your pressure tank bladder has failed.
It's city. I dont have any pumps installed. This loud bang is more than something turning on.
 

LopezBart

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Water hammer happens when a valve is quickly closed; the momentum of the flowing water is converted into a pressure spike; this can cause plumbing to move and make noise. Washing machine and dishwashers can cause this when their valves close. A bladder or accumulator tank is the usual fix. Washing machine outlets often have small pressure bladders as part of the plumbing. The old practice of standpipe above the valves is a short term fix; they usually end up filled with water.
 
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remagenman

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Water hammer happens when a valve is quickly closed; the momentum of the flowing water is converted into a pressure spike; this can cause plumbing to move and make noise. Washing machine and dishwashers can cause this when their valves close. A bladder or accumulator tank is the usual fix. Washing machine outlets often have small pressure bladders as part of the plumbing. The old practice of standpipe above the valves is a short term fix; they usually end up filled with water.
Thanks, I'm googling an accumulator tank now. I'm just hoping its not something else and I'm really not wanting to go crawling in the crawlspace.
 

FrankLee

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The old practice of standpipe above the valves is a short term fix; they usually end up filled with water.
I've got quite a few of those in my house built in 1990. Yes, they can fill with water. You could try to shut your water off and drain your system from, say your outside bib, to empty them if you have them. It's worth a try.
 
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larry_g

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oregon
I've got quite a few of those in my house built in 1990. Yes, they can fill with water. You could try to shut your water off and drain your system from, say your outside bib, to empty them if you have them. It's worth a try.
X2 on this. Costs nothing and may prove that it is indeed water hammer. Shut off the water supply and open ALL of the spigots in the house, high and low and let the water drain. Once drained then turn the water back on and start closing spigots.
lg
no neat sig line
 

Jackfre

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Dec 26, 2010
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N CA
Is there a backflow preventer on the house supply? I have been called out on similar calls. In one case I found that the velocity of water in the main out in the street was creating a negative pressure in the house piping. The reason I was called out was due to a perceived problem with the tankless water heater. With all faucets closed we watched as the negative was pulled on the main and when the flows reduced we would get ghost firings of the water heater Due to the re-pressurization of the piping. It also caused a bit of banging on the associated house piping.
 
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remagenman

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water hammer wont happen when everything is off . above post sounds logical.
also, are you sure it's water related ? is it possible that it's a heating duct that's springing when you walk ?
Okay, this is almost what I also thought. It seems like it happens when I walk across the living room and almost into the kitchen is when it goes off in the hallway area, about 20 feet away?

I mean it shakes and rumbles like a small car hit the side of the house.
 

paulsomlo

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Northern Colorado
If it's water hammer, it'll happen when a running water source shuts off. If it's the furnace, it'll most likely happen as the main burner fires.
 

PCustoms

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Okay, this is almost what I also thought. It seems like it happens when I walk across the living room and almost into the kitchen is when it goes off in the hallway area, about 20 feet away?

I mean it shakes and rumbles like a small car hit the side of the house.
That doesn't sound like water hammer.

Sound like you have a very bad structural issue.

Crawlspace? Can you get under and check the area?
 

3rdgendslmech

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Mar 12, 2017
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Maryland
Is there HVAC duct work in your crawlspace? Asking because not in the crawlspace but up in the upper level of my house depending on the time of year (house settling, how often the hvac runs etc etc) if you step in the right spot it literally sounds like a combination of thunder and an out of balance washing machine.
 
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remagenman

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439
Is there HVAC duct work in your crawlspace? Asking because not in the crawlspace but up in the upper level of my house depending on the time of year (house settling, how often the hvac runs etc etc) if you step in the right spot it literally sounds like a combination of thunder and an out of balance washing machine.
Yes there is. Now I'm thinking it was the cold spell we had that might of done that.
 
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