Key vent replacement question

StorminMike · March 2011

I have a hot water system and recently noticed that one of the ball valves that isolates the boiler for service has developed a pretty good leak. The installer of this particular valve went with a model that has an o-ring on the shaft, so there is no packing nut as such to tighten - I'm told the valve will have to be replaced.

Since I am going to have to get the system drained anyway, I thought I would ask here and see if anyone has a suggestion as to how I might deal with another issue I'm having at the same time.

When the house was built it was piped for a convector in each room. They installed convectors on the first floor, and left the pipes unconnected on the (unfinished) second floor. (They also didn't connect these pipes in the basement). When the second floor was finished years later, styles had changes, so they used baseboard instead. In the master bedroom, at the time, this was about 25 feet of baseboard. At the time, with the R-5 insulation they had, this was actually necessary to keep the temperature correct up there! The supply and return pipes come up along one wall, and the supply is connected to the baseboard there; the return is connected to a second pipe that runs along the top of the fin tube all the way to the other end of the baseboard where it drops down and is connected to the other end of the fin tube.

Getting the air out of this when the system is worked on seems to take forever - I open the bleed valve, and get about 10 seconds of air, followed by a several minutes of an air/water mixture. I don't have this problem in any other room in the house. As one can imagine, this makes quite a mess - the bleeder is very low to the floor so it's tough to catch all the water that comes out.

Is there something I can ask the contractor to change on the piping so this will behave in a bit more friendly manner? Barring that, is there some type of air vent I can use instead of the miniature key activated one that would make it easier to collect all the water that gets spilled when purging this particular loop?

Mike

Brad White · March 2011

I would stick with

a key operated vent and have them install baseboard tees. The automatic vents tend to be too tall to fit in regular baseboard (maybe in commercial baseboard, not residential). I would stay away from the "felt washer" types which rely on the expansion of a felt washer when wet. They sometimes, often enough, form a chronic leak. Ugh.

If no high point key vents, a good purge valve setup (stop valve on the return with a hose-end outlet drain valve just upstream and a similar arrangement in the supply for in-flow), is more common. Think of this as a foray into enema territory.

Provided your expansion tank is in the right place (connected upstream of your circulator), once purged and/or vented, you should not have air problems unless the system is drained for service.

Charlie from wmass · March 2011

Install valves on the feed lines in the basement

Then you can close one side. bleed it and then close the other while opening the first and bleed it. If there is room in the radiator enclosure you could install the valves there but that is doubtful. The issue you are getting is the return or the feed is holding air and the opposite side is bleeding faster. You could also try bleeding it slower this may allow the water to rise in both columns more evenly. As Mr. White said avoid automatic vents as they are an issue waiting to happen.

icesailor · March 2011

Venting upstairs loops:

I'm sure that I am in the minority here. I only put air vents on baseboard emitters to keep nosey mouth's shut. Whatever I do, whatever I pipe, I always plan how I will purge it. I always use "Jet Tees". With the caps.

I do a lot of loop over the top of the baseboard and feed supply and return on one end. No mater how hard you try, it is difficult to get enough air out to get flow going. So, I always have a place on the return where I can connect a hose with a valve below it for purging. Put a ball valve on the return end of this loop with a boiler drain between the valve and the return side of the upstairs loop. To purge the air, just close the ball valve, take a 5 gallon bucket, a short hose (I use a double hose connection like a 6' washing machine hose) and let it go in the bucket. I put the PRV bypass on so it fills past the shut-off point. If you try this, you will need to refine your techniques.

You must be sure to keep the pressure up in the system. I go for 12# to 15# with an emphasis on 15#

Key vent replacement question

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