Blocked riser?

RoiiRaz

Hi all,



I have a one pipe system with two mains. It has a F&T steam trap at the end of each main/return before going into a collector with a pump.



It recently developed some hammering and water spitting from the last convector on one of the two mains. I noticed the trap on that main was staying cool. Figuring it's blocked, I opened it up and cleaned it out -- indeed, found a lot of rust chips inside. The trap is now nice and warm, and I'm getting much smoother and quicker heating.



The problem:



I have one convector on the 2nd floor (off the same troubled main) which has not heated up for years. When I removed the vent, it did warm up, but slowly. I think the old vent was shot, so I replaced it. However, this convector still rarely heats up (even though I can hear some air coming out of the vent now). Another convector in the same room (off the 2nd main) is working fine. After replacing the vent on this one, I started getting some violent hammering in the system again.



My theory is that I have a partially blocked riser on this convector, and that opening it up causes some of the gunk in that riser to wash back into the main and cause problems again.



Does this theory sound plausible? If I do have a blocked riser, what are some known remedies (this thing is in the wall)? I was thinking of removing the vent and trying to pour water into the radiator in the hope of back washing the entire riser.



Thank you for any advice.



-Roii

Jamie Hall

There really isn't much

in the way of gunk which can get into a steam main or riser.  They don't get clogged, as a general rule.



Which is not to say that something isn't blocking the condensate return, thus causing the hammering.  The first place I'd look would be at the valve on the convector which doesn't get warm.  Is it really fully open?  If it seems fully open, is it possible that it has come apart internally and the valve is actually partly blocking the flow?  It does happen.



And, of course, you will have checked the pitch of all the more or less horizontal piping related to this riser... even a short length pitched wrong can create all manner of noise.

RoiiRaz

No valve...

Hi Jamie,



Not much in the way of a valve on this convector. The riser comes off the main, makes a very short turn into a covered (sigh!) basement ceiling, and then into the wall. The next place I can see it is coming out of the floor upstairs right where it goes into the convector.



I was talking about gunk because of the kind of stuff I found inside that main trap when I took it apart -- serious sized rust flakes. I'm wondering if they are coming from that riser, because opening the vent on this convector causes hammering to start in the other convector which had been hammering before. I'm suspecting the rust is coming from this riser and polluting my main.

nicholas bonham-carter

Back washing the riser

You could get some adapters to connect a garden hose to the radiator vent tapping, and flush it that way--NBC

RoiiRaz

Vent adapter for hose...

Any suggestions for a specific type?

steamedchicago

thread sizes

Most radiator vents are 1/8 NPT.  Garden hoses are their own thread, called 3/4 GHT, but adapters exist to let them be attached to plumbing, like a 3/4 GHT to 3/4 NPT.   Go to a hardware store and figure out what you need.  Don't forget you'll need to hook the other end of the hose up to something, and don't forget that you'll probably be working with the male end of the hose at the radiator. 

nicholas bonham-carter

Adapters for hose thread

Most kitchen sinks have an aerator thread on the spout, for witch a garden hose adapter can be found.--NBC

RoiiRaz

Thank you...

...all. I'll give it a shot.