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Old 04-12-2011, 03:31 PM   #1
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Hot water tank t/p valve - plumbed to drain

I am installing a hot water tank (new construction) in my basement. The tank sits next to a wall which has the main waste drain in it. I was thinking instead of extending the t/p valve down to the floor (6inchs above or whatever it calls for) with 3/4 copper, i would use some 3/4 pex, go from the valve into the wall and plumb it in to the drain. If the tank ever malfunctioned and the water was released through the valve then there would be no mess.

Does this make sense? if so what kind of connection fittings would i need to plumb the pex into the 3" drain? would i need to loop the line to create a trap, or would the water in the tank stop the gases?


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Old 04-12-2011, 05:01 PM   #2
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I don't think it's a good idea.

Not only is there a possibility of a cross contamination, but it's probably also not allowed by code. Also check on the PEX connection. Some authorities don't allow that either. It might need to be hard piped with copper.

If it's a finished floor (not concrete) and you don't want the possibility of a mess if it trips; a better option would be to simply install a drip pan and properly maintain the water heater. i.e. drain it out every so often depending on how hard your water is. Also be sure to check your water pressure. If it's over 75psi, either adjust your PRV or install one.

You should also have a floor drain somewhere nearby. Code may require the water heater be placed within a certain distance.


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Old 04-12-2011, 05:29 PM   #3
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you can certainly plumb the t&p into a drain, but it needs to be a separate standpipe that is trapped and vented. do the entire thing in copper and maintain a 1" airgap to prevent cross contamination. the air gap needs to be accessible, so not behind the wall without an access panel over the drain. Also, my code doesn't allow the t&p drain to drain into a pan, and most areas don't like it dumping on the floor near a floor drain.
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Old 04-12-2011, 05:44 PM   #4
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You might want to read the attached before connecting the HW tank to the drain.

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File Type: pdf CCI04122011_00001.pdf (40.0 KB, 235 views)
When its all said and done there is usually more said than done
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