Vacuum Pumps / Trap Maintenance and Water Hammer

ScottF

We have a problem with severe water hammer during the beginning of the heat cycle in a 100 unit, 14 floor building.

A vacuum pump was installed several years ago, where there was none originally and we have been told that this pump is, at least, part of the problem, and may be substandard.

In addition, there appears to have been little to no trap maintenance/repair done in many many years. Besides the F&T traps in the basement, it would be difficult, if not impossible to repair/replace all the traps on the convectors in each unit.

My questions are...

Why would a vacuum pump be installed in a gravity return sytem to begin with (could it have to do with poor trap maintenance)?

and...

Would any "fix" of the water hammer problem have to include trap repair of all the convector traps?

Thank you.

Joe Lambert

If your vacuum system was installed correctly, and you have many failed traps, it would be very hard if near impossible for the vacuum system to actually develop a vacuum. The vacuum return allows the upper floors to heat faster compared to a gravity return in a larger building, thus evening out the heat for everyone.
Also, fixing traps, both the riser F&T's and the individual convector traps probably has the greatest return on investment compared to other improvements in your system. It will also allow the entire system to run better.
As for the water hammer, there are too many potential causes to troubleshoot on a board like this. Call in a professional.