Installing new relief valve.

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Dystantthundr

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Relief valve leaks a little so going to put in a new one. It's an older tank and have seen horror stories of problems after draining the tank. So I'm wondering is it possible to just close the inlet valve, open a hot water faucet and drain enough out that way??

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LLigetfa

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So I'm wondering is it possible to just close the inlet valve, open a hot water faucet and drain enough out that way??
That would not drain below the level of the TPR valve. Connecting a hose to, and opening the drain valve would drain the tank if/when air is allowed in. Lots of plumbers replace even the elements without draining the tank.
 

Terry

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Horror stories? Normally the drain at the bottom works just fine for draining.
Turn off breakers while working on the tank so they you don't "dry fire" the elements.
Water off to the water heater, open a hot tap. If you're replacing the T&P then open that too.
Don't turn the breakers back on until there is a steady stream of water flowing from the hot side out of the tub faucet.

water_heater_drains.jpg


The better water heaters have a brass drain.
 
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Reach4

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You want to flush out the bottom few gallons maybe annually. This can be done while the tank is under pressure. You still might want to combine this with your T&P changing.

The amount you need to drain is going to be more if the T&P is on the side. Mine have been on top, and were gas WHs.

I was not able to use one of those plastic drain tubes. Leaked. I ended up reusing the galvanized drain pipe, even tho with the taller T&P I chose on purpose, the bottom of my pipe ended up a little higher than the required 6 inch max above the basement floor. The good use of galvanized in plumbing IMO is for T&P drains.

I needed to use a lot of torque to take the galvanized apart. I used a large curved jaw locking pliers and a 24 inch pipe wrench. I used both PTFE tape and pipe dope. I also had a large adjustable wrench that I used to tighten the T+P I think, but I did not take notes. I may have forgotten details. You will need to tighten to a position that points the output of the T&P the right way. It does not have to be very tight, but I know that is ambiguous.

ONE MORE THING: if leaking is intermittent, then it is likely due to thermal expansion, and that would mean that you should have a working thermal expansion tank. When water heats in a closed system, and the pressure gets to 150 PSI, it is normal for the working T&P to release water. Cities are adding check valves along with water meters, so as time goes on, more people will need one of those.
 
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Sylvan

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For my better accounts when I install a new heater I remove the cheap valve at the bottom of the tank and install a brass nipple and ball valve with Garden hose adapter (3/4 IPS x 3/4 Garden hose) and place a brass garden hose cap on the threads as a safety precaution

This makes it easier to blow out the sediment
 

Master Plumber Mark

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I do this all the time by just turning off the water to the heater and then relieve the pressure...
You can just unscrew the t+p valve and as long as the new one is the same length or longer
its just a matter of how fast you can pull the one out and put the new one into the hole and
tighten it down...
So you might get a cup full of hot water pour out when replacing the valve with the
water heater full, but I will not fool around and drain down a water
heater just to change the pressure relief valve....

this is how a rookie would do this,
or one of your lazy employees trying to waste the whole day on something stupid....
 

Master Plumber Mark

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Horror stories? Normally the drain at the bottom works just fine for draining.
Turn off breakers while working on the tank so they you don't "dry fire" the elements.
Water off to the water heater, open a hot tap. If you're replacing the T&P then open that too.
Don't turn the breakers back on until there is a steady stream of water flowing from the hot side out of the tub faucet.

water_heater_drains.jpg


The better water heaters have a brass drain.


Those cheap ass drain valaves are typically on Lowes heaters or old whirlpool heaters....
maybe even on STATE or SMITH heaters too......
 
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