Old NRC Boiler suddenly has slow leak from (drain/relief ?) pipe. Why?

Old_Boiler_Owner

I recently had the water pump motor replaced on my NRC boiler. Afterwards a slow drip began from a pipe that extends out from the boiler and has a valve at the top. The drip has increased to where it's a steady trickle coming out. I'm hesitant to try to adjust or move the valve at the top for fear it will make things worse. Anyone know what the pipe is for & why it began leaking?

Thanks!

Gordy

That's the pressure relief valve. It looks quite old may need replaced. However what is the system pressure on the gauge?

lchmb

that is a pressure relief valve. If you pull the lever you will probably make it worse. You need someone to identify why the boiler is over filling with water. It could be the expansion tank is/has failed or the fill device for the boiler is not shutting off properly.. (that device should also be turned to an upright position when it is replaced)

nicholas bonham-carter

It looks like a pressure relief valve. Is there a working gauge on the boiler? This leaking often happens when the expansion tank has become waterlogged, and unable to absorb changes in the system water volume due to expansion as it heats up.
If this is an air cushion tank, and not a bladder type, the procedure, which should be on the yearly maintenance to do list, is to drain the tank, and re-pressurize the system so that there is roughly half the tank of air at the same pressure as the system.
See if you can take a picture of the tank, which is probably in the ceiling of the basement, and post it here.--NBC

Old_Boiler_Owner

Thanks! The expansion tank is right above it. Hard (for me at least) to tell if it's full or not. Valve looks relatively new but I haven't yet opened it any to see if there's any water in there.

Old_Boiler_Owner

Oh, and pressure is ~12 right now. Was checking it regularly for a while after the repair and didn't see it go about ~16

Gordy

System pressure is good. So not to worry there. When checked was the boiler running on a cycle? To see If it climbs as boiler hits high limit

Wondering if who ever replaced the circulator popped the prv when filling by accident, or on purpose, and now it's not seating due to debris.

Old_Boiler_Owner

Was not in heating cycle when that pic was taken. When at ~130º f the pressure was up around 16.

I don't think he did touch the valve, though can't say for sure. Pump is on opposite side and I was with him pretty much the whole time he was doing the work.
I've had same company maintaining it for the 16 years I've lived here. It's usually the same guy too. Motor is only the 2nd repair, every other visit has been annual check. They've earned my trust.

EBEBRATT-Ed

As @Gordy your pressure is ok as long as the pressure gage is reading right.
Your relief valve probably needs replacement and yes as @lchmb it should be mounted with the stem vertical

Gordy

The reason being debris can foul the valve from seating thus leaking.

Old_Boiler_Owner

OK, I opened the valve on the expansion tank and emptied about 5 gallons and there was still more in it. It's a 8 gal tank. It appears it may be refilling from the incoming water line as the bottom of the tank and the pipe running into it are both noticeably colder. And the same amount of water is still coming from the prv. At least as soon as I was done. I'll keep checking it, maybe I'll get lucky and it was just the tank needing emptied.

Thank you guys for your quick & informed replies! This is very helpful

Gordy

Why did you drain the expansion tank?? The system pressure was fine.

Old_Boiler_Owner

I guess I mistook it, despite typing *expansion* to be an overflow tank and needing to be emptied if full. So, it refilling partially would be normal?

If pressure is normal would you think it's likely a bad prv? Anything else to check (that I'd be able to check myself) ?

Gordy

You have to properly fill it. The system needs to be at ambient temp then fill until pressure gauge reads 12psi.

Gordy

Yes replace it, and have it oriented properly. Vertical.

HomerJSmith

Having a bladderless expansion tank, it will fill partially with water after it has been drained until the incoming pressure of the water equals the air cushion in the tank.

The procedure is to turn off the fill to the tank, drain all the water out of the tank and then turning the fill valve on. This is not the fill valve to the boiler, but the fill valve on the line that goes to the tank from the boiler, usually a globe valve.

By the way, the air scoop (that green thing) that removes air from the boiler water needs an Taco 1/8" Hy-Vent. It doesn't work well at eliminating the air without one. My opinion.

It goes in that 1/8" hole where the plug is.

Feeding the air from the air scoop to the expansion tank is probably not as effective as venting to the atmosphere. I know what the original installers were thinking, that the air from the air scoop would displace the water in the expansion tank. Several companies made special valves to accomplish this. That is just my opinion.

I would replace the existing expansion tank with an Extrol 30 bladder tank with a 12 to 15 psi air charge if it is a multi story house. Buy it here: Supplyhouse. com and at the same time replace the 30# pressure relief valve .

These are cheap fixes. Less than $75.

Alan Welch

Thought I read on the Wall you shouldn't use air vent with that tank.

Jamie Hall

Alan Welch said:

Thought I read on the Wall you shouldn't use air vent with that tank.

And you are quite right. The combination of an air eliminator and that type of expansion tank will, in time, deplete the air in the tank. There's absolutely nothing wrong with that type of expansion tank -- provided you keep enough air in it, but not too much.

On the other hand, if you do substitute a bladder type tank, then you have to have the air eliminator.

delta T

You cannot use an air separator with an old style compression tank like that. It is piped correctly as it is, with the vent on the air scoop going to the tank. You want any air in the system to travel to the tank. If there is nothing wrong with the tank then I would not remove it, as if you do replace with a bladder style tank, then you will need to add good air elimination.

delta T

@Jamie Hall You beat me to it!

Gordy

I also understand what the installer was trying to achieve with the air sep. The piping could have been a little more air friendly to get it back to the tank.


I would have teed the water feeder into the side of the verticle pipe going to the compression tank. Used 45's for the offset to make the connection

If you here burbling up into the tank occasionally during a nice heating cycle it's doing the job.

No you should not allow air to escape from the system once purged. Send it back to the tank.

An air trol tank fitting is an asset.

HomerJSmith

I have seen these tanks get water logged with this set up. Having air in contact with the boiler water in a cast iron system is trouble. Oxygen is hydroscopic and you can't keep it out of the water. Why even having an air scoop in this system? Oxygenated water is moving in and out of the expansion tank and moving into the system. I guess the oxygen will eventually bind up with the ferrous metals in the system.

Fred

@HomerJSmith , judging from the age of this system, that tank hasn't been a problem.

HomerJSmith

Just replace the leaking PRV and keep on truckin'.

Gordy

That's why they make airtrol tank fittings.