Manual feed weil McLain boiler refills without adding water??

cquinn091

Hi - first post here. I bought a house in the summer of 2023 and inherited a ~30 year old Weil McClain and single pipe cast iron radiators.

I had minimal issues winter 2023 into 2024 but the first service I did was this past fall (standard cleaning). In any event, this year I have noticed an apparent refilling of the boiler without me actually adding any water. I have on about a half dozen occasions drained the boiler down to a bit above the low level line. Over the course of the next week, the water level creeps back up.

Symptoms of this involve loud banging (guessing water hammer) and the valves releasing air/steam. Once I drain the boiler back down, the noises drastically reduce.

So I just have no real idea how the water seems to come back in when there is no auto feed? My best guess is maybe an extremely slow water return from the radiators due to build up. I suggest this because once the water level creeps back up, it also gets incredibly murky.

I had a second service call with the same company where they replaced the water level viewfinder but the problem persists both before and after. I'm up to almost $1k on the two service calls so I am looking for help.

Other demographic/background:

• House is about 90 years old (1930s carriage house)
• Located in Northern CT

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Jamie Hall

Does this boiler also supply the domestic hot water, either directly with a coil in the boiler or through an indirect water heater? If so, it is possible that that is leaking a little. You can check that by shutting off the hot water on the cold water inlet to the coil or water heater and opening a hot water tap to relieve the pressure. Then watch the boiler water level. If it doesn't rise, that may be the problem.

The other obvious possibility is that the water feed valve is leaking by. They do sometimes. If so, is there another valve in that line of pipe you could shut?

Slow returns will cause the water level to be low for a few minutes to perhaps half an hour after the end of a cylce — but not for longer than that, and they won't cause a slow steady rise over several days or a week…

cquinn091

Hey Jamie - thanks for the reply! Yes this boiler does service the hot water through the house as well (faucets/shower/etc).

By the cold water inlets, would that be these green shutoffs?

and then for the valve leaking do you mean the glass view finder? If so, that was an issue before but hasn’t been since the tech replaced it.

That’s kind of what I figured on the slow return as well!

Thanks,
Conor

cquinn091

sorry - re-read and understand the water valve now. I’ll check if there’s another shutoff before the control right at the boiler.