sight glass question

rather not say

We have a Burham boiler and recently replaced a poorly-installed copper baseboard with a new, smaller-sized upright cast-iron radiator. First we had lots of black gunk that we cleared several times from the boiler. The water looks a bit better, just some brown stuff hanging around. BUT we came home tonight to find the sight glass filled to the top with water. It has never done this before that we know of. When we left the house today it was at the half-way mark. Any ideas?

John@Reliable

One of four things

1.Boiler fill valve not shut off all the way. 2. Valve is leaking by 3. Tankless water heater leaking if you have one. 4. Auto-fill not cycling right if you have one. I find #1 & 2 all the time Hope this helps John@Reliable

jack_4

#5

#5. A blockage or other restriction (pile of gunk) in the returns cleared and has allowed a back log of water to flush down.

Steamhead

#6

It's possible the 1/2-inch pipes coming out from the boiler to the sight glass fittings are plugged. Could be either the bottom or the top one.

If these pipes are steel, they should be replaced with brass ones or the problem will keep coming back.

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rathernotsay

Thanks to everyone for their suggestions! The person who put the radiator in denied the new radiator was creating the gunk (although it started right after it was installed). He then wanted us to pay him more $ to come out and check out the gunk...sigh.

jack_4

Rule to remember

Take a 90 year old system, repipe or replace anything, you will stir up gunk. Expect it. Plan for it, clean it.

rathernotsay

You are so right. And so was everyone else. Found a leaky valve and lots of cleaning that needed to be done.