2 posts / 0 new
Last post
Rain in Walls

I have a radiant heat system with baseboard radiators. The pipes recently began making a noise which sounds like rain in my walls each time the system starts circulating. I have looked for bleed valves on the radiators and on and around the boiler itself and haven't found anything which is obviously a bleed valve. If you have any ideas as to what may be causing this and how to correct it I would really appreciate it.

Re: Rain in Walls


These radiant systems rarely have bleed valves, but instead use what's known as a "purge station" on the return piping, often at or near the return manifolds.

The "rain sound" is a classic symptom of air in the lines that has to be removed.

Several other posters in the past week have posted with this exact same problem.

if you can look under the "Heating" category you will find posts by "froman", "Baseboards not Heating", and others, which describes how there is usually a brass purge valve on the return lines of these piping systems (often near the return manifold).

The boiler is temporarily turned off, a garden hose is attached to the purge valve "hose bib", with the other end placed in a large bucket or plastec barrel.

The off screw or off lever on the purge valve is turned to shut off flow in the zone piping and the "fast fill" lever is pressed on the pressure reducing valve at the boiler, so water (along with the air) is diverted out to the bucket.

The water pushes all the air thru the piping into the plastic bucket.

When no more bubbles are detected in the barrel, the purge valve hose bib is closed, and the zone is again opened.

Each zone has to be done in a similar manner to get all the air out of the system.

Please post back if you can't find the purge valve.

A photo and mode of operation of these valves is below; your purge valve may look slightly different, but they all have a "hose bib" on them that will accept the female fitting of a regular garden hose.

The Bell Gossett site shows a picture of the "fast fill" on the pressure reducing valve.

Enter the Bell-Gossett site & click onto "homeowner" at the top of the page; then scroll down & click onto "valves"; then scroll down to "pressure reducing valves" to get a picture, and operational info; the "tutorial" has additional info on how these valves work.

The little square handle on some of the PRV's is the fast fill handle (on other models, it's a lever).

Also Google "purging air out of radiant lines", or "air purging a radiant system" (with and without the quotation marks).


Sponsored Stories

TV Listings

Find TV listings for This Old House and Ask This Old House in your area.