dripping boiler relief valve

cowie_4

I replaced the boiler relief valve (3/4" 374A) because it was dripping. Upon inspecting the valve I noticed that it was full of crud. Checked expansion tank and found that it was water-logged. Installed new expansion tank (checked pre-charge, set at 12psi). Filled boiler and fired heating system. After getting up to around 180 degrees the relief valve again dripped, not much but a drip none the less. I had the boiler feed shut off the entire time. In my experience, I thought that three things could cause a relief valve to drip; -faulty relief valve, -bad expansion tank or no charge in tank, -or a boiler feed valve that keeps feeding water. (Also an undersized tank. What do you guys think could cause the valve to leak???
Thanks in advance,
cowie.

martin

Relief Leak

You've covered the main reasons for a leaking relief,
what was the pres. gauge telling you while this was happening. Possible a bad new relief but unlikely.

dmy hvac

leak

does uit have a hot water maker?could have small hole and water feeding in that way?good luck im going through a similar problem with a call reliefe valve dripping every few days.

Steve Garson_2

I have seen this happen when the house has a pressure regulator at the water entrance. The solution was another expansion tank on the cold water line.