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Question:

Boiler ? Suggestion to replace Relief Valve -- Do I need to drain boiler First?

Hi,Thank you for all of your help to help diagnose my problem. Now my question is --- when i remove the pressure release valve will water be flying out at me----Since there is not a shut off to that valve for obvious reasons -- should the boiler be brought all the way down (off) then drained before removing this piece...i have a feeling the local home depot may not have this part and I am going to be doing some driving to pluming speciality stores

Answer:

The answer to your question is yes. There is going to be pressure in the boiler and water is going to spray out of the valve if you take it off. Make sure that you shut everything down and drain the boiler prior to doing the repair because the release valves job is to regulate the pressure in the boiler. Please make sure you release the pressure because it could cause serious injury or death if not.
Yes, you must turn off power and drain the boiler to change the relief valve. You need only drain it enough to remove the relief valve without loss of water. Be sure to vent off the air allowed to enter when you restore power. There will be a valve somewhere on the water feed line which will allow you to turn off the incoming water. There will also be at least one drain valve and one or more vents. Vent from the highest point to get as much air out as possible. Your system should have some automatic air vents built into it. That will take care of any air remaining. Be sure your replacement valve is the same as the one taken off. It MUST be the same size and it MUST match the relief capability of the one being replaced.
There has to be a valve on the water supply line. Close it turn off the heat source and let the system cool. Drain off enough water to reduce the pressure to 0psi in the system. Then when you have the replacement at hand, remove the old, install the new one with only a little water lost. Use teflon tape or thread compound to avoid leaking. Refill the tank to the proper level, vent any excess air, then turn the heat source back on. You may get some rumbling as the air in the new water is worked out and you may have to vent it if there is too much. This is not a job for a rank amateur, but with some experience and care you can do it. Be careful, an exploding water boiler is a dangerous thing, that is why they have pressure relief valves.

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