I shut the water the off to my hot water system and I drained my boiler through the drain valve to replace circulating pump and pressure relief valve that were very old. No problems. I have an old American Standard Boiler. I went to turn the water back on, but system did not refill. I know the valve is good, recently upgraded. I am stumped why it won't refill. Since system is old should I try to refill back through the boiler drain vale? Any help would be appreciated. Thank you.

If you KNOW that the valve is actually open then the only other explanation is that you have no air vent open at the top of the system

OR

an 'auto-fill' PRV valve is inoperative.

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"Measure Twice & Cut Once" - Retired U.A. Local 1 & 638

I would tend to think the auto fill also hopefully you changed the temp/ pressure gauge while the system was empty also

as my friend from SC surmised.

mosy likely the auto fill valve is stuck closed. it is a common problem.

it will need to be replaced.

as a tempory fix you can back fill it through the boiler drain valve. a washing machine hose will do the trick.

watch the pressure gauge. don't let the system get above 30 PSI or the relief valve will blow.

once full, set the pressure to 12-15 PSI.