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AR15.COM
8/11/2016 8:35:57 AM EDT
So this has been happening since we bought the house back in 08. Never really thought about it much until today.

I have 2 upstairs bathrooms. the sinks ( may be shower and toilet as well but the shower is always set on the warm side and I never stick my hand in the toilet)
Will sometimes have hot water coming out when the cold side of the spout is turned on. It will last anywhere from 1-5 minutes, then it will get cold.
The hot side is always hot, it never starts or turns cold.

Any idea on what may be causing this?
8/11/2016 8:37:51 AM EDT
[#1]
needs a check valve on the hot water heater......
8/11/2016 8:46:17 AM EDT
[#2]
Mixing valve leaking by?
8/11/2016 8:52:45 AM EDT
[#3]
Is your shower valve turned on, with a handheld sprayer turned off?
8/11/2016 8:52:58 AM EDT
[#4]
Quote History
Quoted:
needs a check valve on the hot water heater......
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We have an oil fed burner.

Again this is only 2 sinks upstairs that I know of (toilets and showers) I will check on them latter today
8/11/2016 8:53:29 AM EDT
[#5]
Quote History
Quoted:
Is your shower valve turned on, with a handheld sprayer turned off?
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No, we do not have that style shower
8/11/2016 9:07:33 AM EDT
[#6]
Quote History
Quoted:
needs a check valve on the hot water heater......
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Although that might work, I've never heard of such a thing.

I'd look for a plumbing error around the water heater.  It sounds like there might be a tee in the wrong place, the water heater is plumbed backwards, or a valve is open where it shouldn't be.
8/11/2016 9:10:03 AM EDT
[#7]
how often does it do it --like every time you turn on the faucet or only after it sits unused for any period of time.
8/11/2016 9:15:43 AM EDT
[#8]
maybe you have a HW pipe running for some distance in contact with the CW side.


8/11/2016 9:16:24 AM EDT
[#9]

Quote History
Quoted:


Mixing valve leaking by?
View Quote
Mixing valve at the shower faucet is bad. Not an uncommon thing to happen, back feeds the cold water line.



There is an Ask This Old House episode on it if you do some searching.



 
8/11/2016 9:24:11 AM EDT
[#10]

Quote History
Quoted:
how often does it do it --like every time you turn on the faucet or only after it sits unused for any period of time.
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Quote History
Quoted:
how often does it do it --like every time you turn on the faucet or only after it sits unused for any period of time.


After it sits overnight or during the day with little or no use



Quoted:
Quoted:
Mixing valve leaking by?
Mixing valve at the shower faucet is bad. Not an uncommon thing to happen, back feeds the cold water line.

There is an Ask This Old House episode on it if you do some searching.
 


Well the bathroom is being renovated next month. I hope this is it.

nothing like brushing your teeth with surprise hot water.
8/11/2016 9:24:38 AM EDT
[#11]
Like others have said, mixing valve.
8/11/2016 9:39:26 AM EDT
[#12]

Quote History
Quoted:


Like others have said, mixing valve.
View Quote
Yep; not uncommon I've replaced a couple in my house.



 
8/11/2016 9:41:24 AM EDT
[#13]

Quote History
Quoted:
After it sits overnight or during the day with little or no use
Well the bathroom is being renovated next month. I hope this is it.



nothing like brushing your teeth with surprise hot water.

View Quote View All Quotes
View All Quotes
Quote History
Quoted:





Quoted:

how often does it do it --like every time you turn on the faucet or only after it sits unused for any period of time.




After it sits overnight or during the day with little or no use
Quoted:


Quoted:

Mixing valve leaking by?
Mixing valve at the shower faucet is bad. Not an uncommon thing to happen, back feeds the cold water line.



There is an Ask This Old House episode on it if you do some searching.

 




Well the bathroom is being renovated next month. I hope this is it.



nothing like brushing your teeth with surprise hot water.



http://www.thisoldhouse.com/how-to/how-to-repair-shower-anti-scald-pressure-balancer



This is the one...



 
8/11/2016 9:43:48 AM EDT
[#14]
Quote History
Quoted:
Mixing valve at the shower faucet is bad. Not an uncommon thing to happen, back feeds the cold water line.

There is an Ask This Old House episode on it if you do some searching.
 
View Quote View All Quotes
View All Quotes
Quote History
Quoted:
Quoted:
Mixing valve leaking by?
Mixing valve at the shower faucet is bad. Not an uncommon thing to happen, back feeds the cold water line.

There is an Ask This Old House episode on it if you do some searching.
 


Correct.

If it is a faucet that is bad, you can get a check valve on the cold side to stop it.

If it is the shower, New cups may stop it. It just depends on the design.
8/11/2016 10:40:07 AM EDT
[#15]
Quote History
Quoted:


Although that might work, I've never heard of such a thing.

I'd look for a plumbing error around the water heater.  It sounds like there might be a tee in the wrong place, the water heater is plumbed backwards, or a valve is open where it shouldn't be.
View Quote View All Quotes
View All Quotes
Quote History
Quoted:
Quoted:
needs a check valve on the hot water heater......


Although that might work, I've never heard of such a thing.

I'd look for a plumbing error around the water heater.  It sounds like there might be a tee in the wrong place, the water heater is plumbed backwards, or a valve is open where it shouldn't be.


Commercial hot water systems always have a check valve for that very reason. If it goes bad, we get hot water on the cold side.