Losing Hot water when I Flush.


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Old 11-07-10, 08:21 AM
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Losing Hot water when I Flush.

Hi

I have an odd problem. Whenever I flush my toilet I hear a loud BANG in the basement and for some reason i lose Hot water from the tap. and it stays off until the toilet tank fills up. The cold water works fine(pressure goes down a bit and goes to regular pressure when tank is full).
It seems like the water heater is being starved. But what about the Bang. I've heard water hammer occurs when water is being shut off, but this is happening when the tank starts to fill.

I recently remodeled this bathroom and replaced all the fixtures. So everything is brand new. The plumbing itself is all the same.
I hope some one has an idea on how I can fix this.

Thanks
Sam
 
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Old 11-07-10, 12:49 PM
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Sam, welcome to the forums! Little background first. How big is the water supply to the house and is it copper, iron or pvc. Should be 3/4". You take off that at every turn up to an appliance with 1/2". Each appliance will use a 3/8" supply line. SO, in essence at each appliance you are using 1/2 of the supply of the cold and hot water supplied by the 3/4" pipe. This should, in theory, not cause a reduction in pressure to any given appliance, say you are in the shower and someone flushes a toilet.
Let us know what you got, and we'll serve again.

Larry

"Half of communications is listening, and you can't listen with your mouth"
 
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Old 11-08-10, 03:50 PM
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Yes it is just like you said

3/4" copper coming in and then branches off to 1/2"

I do not lose water pressure any other time. it's just when I flush the toilet I hear the pipes bang and The hot water turns off completely until the tank is full.
 
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Old 11-08-10, 06:28 PM
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Hot water turns off completely, where? At all faucets? Shower alone? List all the changes you made to the piping when you remodeled. Are all you stop valves under the sink and at the toilet turned on all the way? Did you hook up hot water to the toilet by mistake?
Sorry for the questions, but as you can see no one else has heard of this problem, either.
 
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Old 11-08-10, 07:05 PM
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How close is the water heater to the toilet and is it lower or higher than that unit's "water closet"...
But I cannot see how this can happen..
 
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Old 11-09-10, 08:24 AM
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I didn't change any of the piping. I changed the toilet, the faucets and the entire shower assembly. The new toilet fills really fast and I was wondering, is it possible that it could be siphoning the supply to the water heater, hence losing the hot water. Yesterday I turned the supply to the toilet down to half and the problem doesn't seem to happen.

Oh ya...About a week ago I lost the hot water completely and it wouldn't come back on. I'm not sure if it happened when the toilet flushed. My wife just went to use it and there was nothing. This was all the taps throughout the house. The cold water was fine. Did some research online (since it was in the middle of the night) and found that I had an "Air Lock" Learned how to fix and all was good

Earthworm..The toilet is on the main floor and the water heater is in the basement. They are kinda close to each (approx. 10 feet), but the sink is closer and the shower is really close (right above the water heater)

what if I installed an inline check valve somewhere?

Oh and by the way. If you guys are looking for some to present problems that You've Never Heard Of, I'm the man for the job.

Thanks in advance
Sam
 

Last edited by Samgaz; 11-09-10 at 09:06 AM.
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Old 11-09-10, 04:11 PM
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You don't want to put in a check valve. It is doubtful the 3/8" supply line to the toilet would overpower the 3/4" line into and out of the water heater. How old is the water heater? Did you say the cavitation problem was solved??
 
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Old 11-09-10, 04:14 PM
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So, I asked the wife for advice..
This is a very common problem - when a man takes a shower, NEVER turn on the cold water, or hot water or anyplace else....unless its part of a practical joke...lol....but we never had any "bang" or "pipes hammering".
A check valve in the right place or a restriction at the toilet supply is the solution...
A really smart plumber would know where to install a check valve...
 
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Old 11-09-10, 05:50 PM
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The water heater only has a 1/2" supply and it is only 2 years old. Not sure if the cavitation has been solve. i read online that i had to connect a hose from the cold water tap to the hot water tap and run the cold water through the hot water line. I did this and it got rid of the Air lock. and the hot water was back.

Do you know what causes an Air lock?
 
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Old 11-09-10, 07:12 PM
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1/2" supply is too small. The WH came from the factory with a 3/4" inlet and outlet. Why was it defeated? I thought you reported there was 3/4" lines throughout with 1/2" lines to fixtures.
Earthworm, what prompts you to say a check valve will solve the problem? What part of the system will you check?
 
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Old 11-10-10, 06:28 PM
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Maybe the check valve idea was not so good. I vaguely remembered a check valve being used to keep the hot and cold water separate at a water heater....more research is needed.
The 1/2" works for me, the whole system is but 1/2".. no doubt that the 3/4" is better..
Probably 50 million homes in America are under-plumbed.
Maybe the OP just needs a restrictor.
Or an expansion tank in the water supply system, these I have seen...so there must be a reason for this expense.
 
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Old 11-10-10, 08:34 PM
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Some states mandate an expansion tank on the cold water side of the water heater. It definitely wouldn't hurt to install one. It would keep the banging down, at any rate. Still don't know why the hot water quits when the OP flushes a commode.
 
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Old 11-11-10, 05:46 AM
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I am in Canada and anywhere I've lived the water heater has always had 1/2" and 1/2" out. The water heater is equipped for 1/2" and it was installed by the gas company. The plumbing code here must be bifferent.

I Still think that the Air lock problem is connected to this. I just have to figure out what causes an airlock
Earlier I changed the plumbing in the basement bathroom. I added a shower. But never had any problem after that.
So I never connected it to this problem in the upstairs Bathroom.

I still have the water supply to toilet only half open and still the problem hasn't happened

I have never heard of using an expansion tank. I'll have to look into that
 
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Old 11-11-10, 09:48 AM
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Different plumbing configurations require different things(valves, sizes,tanks).
And of course, the 2010 code is upgraded from the 1810 code.
Pick up a good book or manual on this subject or hire a hyraulics engineer...
The toilet water supply should be 3/8", but NOT galvanized...ask how I know....we have acidic high mineral content water...
 
 

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