Water Heaters - Water Heater T&P goes uphill
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sehenry2000
12-12-05, 11:08 PM
I have an electric water heater in a closet of a bedroom, in the center of the house. The T&P valve discharge goes up into the attic, across to an outside wall and down the wall where it goes outside. I'm selling the house and an inspector for the buyer says I have to raise the water heater 18" because of the T&P valve. Why? It's not in a garage so the 18" rule does not apply. He mumbled something to the buyer about siphoning and contaminating the water supply??
majakdragon
12-13-05, 01:13 AM
sehenry2000, Welcome to the DIY Forums.
I have never seen aT/P valve discharge run uphill. As far as the inspector, if he puts it in a report to the buyer (even though it was verbal before) make him show you where he got that idea. What would it siphon, AIR? Good luck.
I have never seen aT/P valve discharge run uphill. As far as the inspector, if he puts it in a report to the buyer (even though it was verbal before) make him show you where he got that idea. What would it siphon, AIR? Good luck.
hankhill6018
12-13-05, 03:55 AM
To my knowledge the 18 inch rule only applies in garages. I have never heard T&P valves being piped upwards. In order to properly expell the excess pressure build up, there would need to be enough pressue to discharge the water all the way through.
As far a siphoning and contamination of the water supply. Are you on a public water main? Some codes require a check valve where the water line enters the structure for this reason. This should have nothing to do with the water heater itself.
As far a siphoning and contamination of the water supply. Are you on a public water main? Some codes require a check valve where the water line enters the structure for this reason. This should have nothing to do with the water heater itself.
Pendragon
12-17-05, 08:52 PM
I have an electric water heater in a closet of a bedroom, in the center of the house. The T&P valve discharge goes up into the attic, across to an outside wall and down the wall where it goes outside. I'm selling the house and an inspector for the buyer says I have to raise the water heater 18" because of the T&P valve. Why? It's not in a garage so the 18" rule does not apply. He mumbled something to the buyer about siphoning and contaminating the water supply??
The IRC says that the T&P must drain by gravity and cannot exit more than 6" above floor level.
This A. keeps water from being trapped in the piping (the discharge line cannot be trapped) and B. keeps boiling water from potentially being discharged onto someones head.
Keep in mind that this rule may not have been in place when the home was built.
The 18" rule doesn't apply because it's not in a garage and gas fired and has nothing to do with siphoning.
The IRC says that the T&P must drain by gravity and cannot exit more than 6" above floor level.
This A. keeps water from being trapped in the piping (the discharge line cannot be trapped) and B. keeps boiling water from potentially being discharged onto someones head.
Keep in mind that this rule may not have been in place when the home was built.
The 18" rule doesn't apply because it's not in a garage and gas fired and has nothing to do with siphoning.
sehenry2000
12-18-05, 07:43 PM
Maybe I wasn't clear. The discharge pipe goes down an outside wall to grade, pops out the wall and then elbows down about 6" from the grass. That part is done correctly even though there is no nipple in the ell. It's not supposed to end in a threaded connection so nobody gets the bright idea to plug or cap it. But what does trapping 6' head of water (< 3 psi head) hurt? Normal water pressure, much less a T&P going off at 150 psig, should push up, over and out OK. Is it just a code thing with no real justification? Thank You
notuboo
12-19-05, 06:48 AM
It is a code thing and a safety thing. For those wanting the code thing, look at P2306.3.1 of the International Residental Code.
This falls under 2 seperate parts within this particular section of code. The discharge line shall not be trapped and the discharge line shall drain by gravity.
Any back pressure on a spring loaded valve, even though it is a small back pressure, it still a bad thing. The valve is built and has a spring load to relief pressure. Any back pressure just raises the operation pressure of the valve. 6 feet of water may not be a big deal, but it could be the difference of the valve opening when it should or a problem developing.
18 inch rule stated earlier has some provisions, none of which apply to you. It is mainly for gas fired water heaters in garages and hazardous areas not in direction connection with the living space of a residence.
What to do... not an easy answer if there are no convient floor drains. Raising it may the only option unless moving it to another area of the house would be easier/cheaper.
Good luck with your project...
I added this later as an after thought:
Dunbar (steve) lives in an area that does allow trapping of T&P lines AND he has pics to prove it. If he chimes in on this, throw out everything about traps and drainage. I don't understand why it is allowed, but it is. This is a very local issue for that area of the country.
This falls under 2 seperate parts within this particular section of code. The discharge line shall not be trapped and the discharge line shall drain by gravity.
Any back pressure on a spring loaded valve, even though it is a small back pressure, it still a bad thing. The valve is built and has a spring load to relief pressure. Any back pressure just raises the operation pressure of the valve. 6 feet of water may not be a big deal, but it could be the difference of the valve opening when it should or a problem developing.
18 inch rule stated earlier has some provisions, none of which apply to you. It is mainly for gas fired water heaters in garages and hazardous areas not in direction connection with the living space of a residence.
What to do... not an easy answer if there are no convient floor drains. Raising it may the only option unless moving it to another area of the house would be easier/cheaper.
Good luck with your project...
I added this later as an after thought:
Dunbar (steve) lives in an area that does allow trapping of T&P lines AND he has pics to prove it. If he chimes in on this, throw out everything about traps and drainage. I don't understand why it is allowed, but it is. This is a very local issue for that area of the country.
Pendragon
12-19-05, 07:52 AM
Dunbar (steve) lives in an area that does allow trapping of T&P lines AND he has pics to prove it. If he chimes in on this, throw out everything about traps and drainage. I don't understand why it is allowed, but it is. This is a very local issue for that area of the country.
My area doesn't require the T&P to exit _outside_, it can discharge into the crawl space under the home.
The IRC (and others) is just a guideline, your local area can use pretty much any set of codes it wants, or make some up if it doesn't like the ones there.
My area doesn't require the T&P to exit _outside_, it can discharge into the crawl space under the home.
The IRC (and others) is just a guideline, your local area can use pretty much any set of codes it wants, or make some up if it doesn't like the ones there.