Pressure relief valve lifting on hot water tank

[LazyPup]

Whenever i install a new water heater i make it a point to remove the plastic drain valve and replace it with a brass 3/4 inch boiler cock.

I also thoroughly examine the shut off valve and if in doubt replace it with a lever type ball valve. In addition, i install a second ball valve on the tank discharge side. By installing valves on both the supply and discharge side it permits complete isolation of the tank and precludes the necessity of draining the entire hot water side of the house during future heater change outs. The total cost of the three valves is well under $20 and if one is careful to explain the reasoning to the homeowner I have found they all appreciate the extra steps.

[jobrien712342]

My pressure relief valve recently started leaking some, then alot. I followed the advice in this post and have replaced the T+P valve. I also picked up a water pressure gauge, hooked it on the water heater drain and turned the water back on. PSI without heating the water ranges between 100-105. Still without heat, I ran the hot tap, then abruptly shut it off and PSI bounced up to 120 temporarily. So I have two questions:
1: How bad is my PSI? Quit typing and fix it now, or fix it in a month or so?

2: How do you calculate the PSI when heating water?
I've seen somewhere that said +5 PSI for each degree over 75 degrees fahrenheit, but I cannot imagine that is correct.

--thanks
--joe

[John Sprung]

> Whenever i install a new water heater i make it a point to remove the plastic drain valve and replace it with a brass 3/4 inch boiler cock.

That sounds like a good idea. I've heard it before elsewhere. But where do you get a boiler cock? Is there a make and model to ask for? I've used an ordinary ball valve, but it developed a slow leak.

-- Thanks




-- J.S.

[John Sprung]

quote:Originally posted by jobrien712342

PSI without heating the water ranges between 100-105.

That's high, do you have a regulator? If so, it may be stuck or leaking internally. Domestic water should typically be about 40 - 50 PSI. Maybe up to 60 PSI. I get about 110 - 115 ahead of my regulator.

Heating the water will cause it to expand and increase pressure if the system is closed. But if you have no regulator, all it does is push a tiny amount of water back up the pipes. It can't increase the pressure beyond what you get from your utility company. On a regulated system, you can put an expansion tank on the cold side, usually near the heater. The tank is sort of like a water hammer arrestor on a grand scale. It's a little smaller than a 5 gallon bucket, and has a rubber diaphragm in it. One side is connected to the cold water, and the other is pre-charged with air to about 40 PSI. This gives the expanding water someplace to go, and reduces the pressure increase to nearly nothing. It's sort of like having springs and shocks on a car instead of having the body bolted firmly to the axles.

If you put in an expansion tank, consider putting a permanent pressure gauge near it. You can do it for well under $20, and any time anything strange happens with water, you can check the pressure immediately and conveniently.




-- J.S.

[LazyPup]

John Sprung

Under normal circumstances there should be enough expansion capacity in your water hammer arrestors to compensate for thermal expansion of the water and there should be no increase in line pressure, however100 PSI is definitely tooo high.

The International Residential Code (IRC 2903.3.1) and the Uniform Plumbing Code (UPC608.2) require a pressure reducing valve on the water main whenever the pressure to the building exceeds 80psi.

When the pressure on the main exceeds 80psi you are also required to have an expansion tank on the cold water supply line immediately before the water heater vessel. (IRC2903.4) (UPC 608.3)

In regards to boiler drain cocks,,you can find them in any hardware or big box home supply plumbing dept. They are usually located close to the outside hose bib faucetts. Boiler cocks have the advantage that they are a full bore valve which will effect a better flush.

Also when flushing a tank, first ,,,MAKE SURE THE BURNER IS TURNED OFF or if an electric tank, make sure the electrical breaker is turned off. If a burner comes on while a tank is empty it will do severe damage to the vessel or in the case of electric tanks it will burn out the heating elements.

Attach your hose to the drain cock and run it ourside or to a suitable drain, then open the drain cock and allow it to flush for two to three minutes before turning the water heater supply valve off, that will give it a good forced flush. ( what is known in the boiler trade as a -Blow Down).

Once you turn the cold water supply off, open a hot water faucett in the kitchen or bathroom to allow air to vent in, which will allow the tank to drain quicker.


When the tank is drained, close the tank drain and open the cold water feed line. Keep the kitchen or bath faucett open to vent air as it fills.

Allow the tank to sit idle for 30 min to an hour to allow any sediments to settle, then open the drain valve again to flush that sediment.

Close the valve, remove the hose and relight the burner or switch the electrical breaker on.

[John Sprung]

quote:Originally posted by LazyPup
In regards to boiler drain cocks,,you can find them in any hardware or big box home supply plumbing dept. They are usually located close to the outside hose bib faucetts. Boiler cocks have the advantage that they are a full bore valve which will effect a better flush.

Where are you located? I'm in Los Angeles, and here the big box stores have never heard of a boiler cock. They want to sell you another one of those plastic OEM bibbs that won't last any longer than the one you're replacing.



-- J.S.



-- J.S.

[Dean]

Maybe that's because people that work in the "big box stores" are not well versed in plumbing terms.

We call them "boiler drains" and keep them in stock in both 3/4" MIP to use for water heater drain valves and 1/2 MIP versions for laundry washing machine valves. We buy our inventory from plumbing wholesale houses but I would think most people that work in a real hardware store will know what a "boiler drain is.

The problem sometimes is that they aren't long enough to reach through the water heater jacket/insulation so we use a 3/4" angle female sill cock with a brass nipple instead.