Water hammer???

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  #1  
Old 07-21-07, 07:25 PM
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Water hammer???

I have a small thumping noise coming from the flexible copper pipe the feeds cold water into my water heater. It happens when ever the toilet fills or a faucet is turned off quickly( hot or cold). I tried one of those small water hammer arresters at the toilet it helped some but the noise is still there. The flexible pipe happens to be the highest point of the plumbing system. The pipe comes out of the wall behind the heater and their is a gate valve and then the pipe is shaped like a upside down U and goes into the water heater. The pipe does not jump or move. Oddly if you shut off the gate valve the noise stops. Is this a big problem that I should call a plumber or is there any fixes I could do. I can live with the noise if it is harmless. I checked my water pressure and it is 76psi.
 
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Old 07-22-07, 09:45 AM
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So then what is striking you odd is the fact that since your water forks off your mainline BEFORE the water heater, that when you shut off the gate valve to your water heater the thumping no longer will occur when you flush the toilet?, so therefore you don't know what your water heater has to do with it? since no hot water is in the equation?

Try this: Try to run just a trickle of hot water just beyond the water heater from some faucet. Then when the toilet is flushed, see if not only that the sound reduces or stops, but also that trickle suddenly behaves like it just got a power power boost behind it. IF so, maybe that would indicate you have a check valve - somebackflow preventer - keeping your house from backdraining to the city service? and then when you flush the water and the water comes to a sudden stop it has nowhere to go other than to 'charge' the water logged water heater with more pressure and cause the hammer sound. Maybe.
 
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Old 07-22-07, 12:11 PM
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I opened a hot water faucet a little and flushed the toilet. Yes I did here the noise and yes the water did jump up in pressure a bit. I don't think I have a check valve in the system unless it's in the water meter.
 
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Old 07-22-07, 12:28 PM
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Do you have good water volume in your house? One indicator of this is when you say flush a toilet, does it sort of kill the water pressure to a sink? Is your house plumbing all copper? Where is the toilet in relation to the water heater and how many floors is your house?
 
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Old 07-22-07, 01:52 PM
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Thanks for your help ecman51. Yes I would say I have good water volume. I never hesitate to flush the toilet before I take a shower. The plumbing is all copper on a 1950's ranch house on a slab. The water heater is in the middle of the house and the toilet is in the front and the water comes in the front.
 
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Old 07-22-07, 02:02 PM
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It sounds like either you are just going to have to add another water arrestor or two, or you could simply slow the flow to the toilet fillvalve by closing down the shut off valve under the toilet some, as you must have water entering that toilet at a high rate of speed, I'd imagine, for this to be happening. (Why didn't I think of this before? )
 
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Old 07-22-07, 02:14 PM
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The noise does not bother me too much except for the fact that I think something is going to break? But because I does not seem that the pipes are jumping could I be damaging anything or is it just a annoyance? If I add another arrester should It be at the water heater where I here the noise? One more thing the valve in the toilet is a fluidmaster and I here that they are known to shut off quickly. I don't see a way to adjust the shutoff so is there another brand that has more of a gentle shutoff?
 
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Old 07-22-07, 02:46 PM
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Yes, the Fluidmaster can shut off abruptly. But don't you have a shut off valve UNDER your toilet where the supply line comes through the lower wall or floor? THAT is what you would shut down - perhaps to the point that it takes about 30 seconds or so to fill the toilet tank back up.

I am still in the process of trying to think why YOUR house, as opposed to other houses, are having this problem, though. I have worked on houses with 100 psi pressure and not have this. Could it be that this hammer noise is caused more by resonation of pipe hitting against somewhere you can't see it, like where it passes through wood?
 
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Old 07-22-07, 02:51 PM
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Angry

Thanks for the idea I turned down the valve as it is still the same.
 
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Old 07-22-07, 03:06 PM
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This is interesting. Just how far do you have to close the valve before you no longer get that hammering?

What size is your house's main trunk line and how big are the pipes that go off to the fixtures, before they reduce say to 3/8? And DO you have 3/8 going to the toilet tank after the shut off valve?, or is it larger? And did you slow the toilet fill to 30 seconds? Try for 1 minute.

Are you on a well system? (that would have a check valve preventing backflow) You say you have 78 psi, but I have to ask anyway.
 
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Old 07-22-07, 03:21 PM
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Pretty far down. It is just trickling in. I guess the water hammer arrestor I have on the bottom of the toilet is not doing much. http://www.siouxchief.com/Frm_NS.cfm
 
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Old 07-22-07, 03:27 PM
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I am perplexed and now will be thinking about this tonight, wondering why YOU have this and not everybody else. But you never answered me if you have a well. Have to know that. IF say you had a well, and your pressure tank was water logged, then I could really see this happening.
 
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Old 07-22-07, 04:11 PM
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No it's city water. One other odd thing. A few weeks ago I turned off the main valve, opened all the faucets and let the whole house drain. I read this recharges air gap system. The noise was gone for a day. Also sometimes when nothing is running I can here it faintly, and yes I it is the same noise and pipe. Could it have something to do with the water heater changing the pressure of the pipes as it cools or heats up, and because the flex pipe is the highest point there is so air in there compressing and expanding.
Also is this a problem that requires a plumbers attention before something breaks?
 
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Old 07-23-07, 06:55 AM
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IF you for SURE do not have a pressure reducing valve at the entry to your house, nor some check valve - and you may want to ask the city if they put in some kind of check valve in their lateral service - AND the city's pressure tank has not been neglected and is in it's own right water logged - that if none of these potential problem causing things exist, then you have a house set up like the many ones I work on where this problem like you are experiencing does not exist in any of ours. BUT many of these homes have a water hammer arrestor at the dishwasher and at the laundry pipes (for a total of 3), and could very well be dampening water hammer for other plumbing uses as well. It's possible you may need to add another arrestor or two, as these are pretty small ones.

You may THINK that u-pipe would actually serve as another water hammer arrestor. But after time, with a bladderless arrestor, the air that may have been in it becomes taken out by the water. The other oddity is that this pipe does not shake when you hear that hammer sound.

What SHOULD be happening is even IF say your water heater was getting too hot, that the extra pressure created should be able to find it's way out the cold inlet pipe and force the added pressure up the city water line.

Can you ask your neighbors if they have such a problem as well?

Is there anything odd at all about the plumbing sizes in your house or if someone pieced in a smaller diameter pipe in the line, or something? Most houses have 3/4 inch mainline with 1/2 inch lines that branch off to go to different fixtures. What size is that u-shaped pipe?
 
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Old 07-23-07, 07:41 AM
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Originally Posted by ecman51` View Post
Is there anything odd at all about the plumbing sizes in your house or if someone pieced in a smaller diameter pipe in the line, or something? Most houses have 3/4 inch mainline with 1/2 inch lines that branch off to go to different fixtures. What size is that u-shaped pipe?
Now that I think about it...
The main water pipe into the house is 3/4. It is not the original pipe all my neighbors had their main replaced years ago. Ours was done well before we bought the house. The 3/4 pipe enters the garage and connects to the cold water pipe of the laundry sink. From what I can see the laundry pipe is 1/2 inch( there is a small hole where the pipe enters the slab under the sink). All the other pipes in the house look to be 3/4 inch. (most pipes feed into the slab) . So YES the main comes into the house then is reduced to 1/2 inch for a few feet and then go back to 3/4 inch. The faucet at the laundry sink used to make the noise till I put a water hammer arrestor on the washer outlet, now its quiet. So to sum it up I have 3/4 inch pipe them 1/2 for a few feet them 3/4 the water heater and flex tube is 3/4 and so is the toilet.
We really were not planning on any major projects for a few years we moved into the house 4 years ago and it need a lot of work and we are still trying to recover from all the money we spent when we moved in. Can we live with the noise or is it a ticking time bomb?
 
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Old 07-23-07, 03:26 PM
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Originally Posted by Dimme View Post
. Can we live with the noise or is it a ticking time bomb?
Excuse me if I jump in here a little. I've seen water hammers in factory steam lines you'd think were going to blow the roof off the place or knock the wall down and they did it every week at start up time.

It's not good but thank God I've never seen one actually knock the end out of the line so far as you might expect any minute from the way they sounded.

In my judgement if you even wonder about it, I doubt it's causing any real damage. In fact it sort of sounds more like the ticking temeperature changes in a pipe on a wire or metal hanger unless you can make it tick repeatedly by opening and closing a valve repeatedly. If so then the problem is for sure a water hammer and pretty easy to fix.

The longer the line the worse the hammer will be and you just need more cushion at the end. I've seen water lines many times with more than one cushion at the end.

One option the old timers used was to just put a T at the end of a line instead of a 90 and just run a dead end pipe straight up and cap it. Air collects there and will compress instead of hammering the the valve. The more cushion you need the taller the dead end line.
 
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Old 07-23-07, 03:28 PM
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Maybe that's it; the 1/2 inch pipe. Maybe when you suddenly shut off water the sudden surge tries to send water backwards, and when it hits that reduced 1/2 line, from being pushed by 3/4 inch water, that has something to do with it. You may want to install an arrestor right by this area, perhaps.
 
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