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Leading cause of water hammer at startup is ...

brian_27 Member Posts: 7

Through this site and the Wall I've really improved the functioning of our 2-pipe steam system. Lately - and I swear this has changed over the past few weeks - I'm getting pretty bad water hammer on startup. The original install on our 80 year old house only dripped the mains, so there are no dripped risers. If I may:

(1) if the risers aren't dripped the line should be sloped back into the main, and the main should be sloped back to the F&T at each main (mine has two mains off the boiler), right?
(2) water hammer at startup is mainly due to water sitting in the main/riser OR failed/nonexistent traps in the radiators which put steam into the return?
(3) dry returns that have lost their correct slope back to the boiler room will become wet returns and (true or false) will cause water hammer.

SO I should really focus on the sloping of the risers/mains, right, and possible add a trap to those that can't be corrected?




  • Weezbo
    Weezbo Member Posts: 6,232

    as fun as it is to do all the work ...what about hire a professional to stop by...he will likely be quickly able to appraise the actual deal going on ...some times buildings settel a bit and well,alot of other thing he would see faster and know...that way you get the low down on whats happening quicker and if your any good at it maybe he could use some help on saturdays:)
  • Brian in Indy
    Brian in Indy Member Posts: 15

    If only it were that easy. The pros who give unselfishly on this board need to remember that not everyone is being cheap, some of us can't find anyone capable of working on a residential steam system. I'd love to have a savvy, honest steam pro come by!

    The commercial boiler company came by and replaced some buried returns ($3K). Used too many 90's, were kind of expensive. Wanted to install a boiler feed tank/pump to replace the condensate receiver ($5K) without even hearing/seeing the system run. Wasn't interested in seeing the original design blueprints when Hoffman engineering installed the system in 1935. $250 per radiator to troubleshoot/repair as required.

    Referred to another company, real nice guy, actually measured most of the radiators and looked at the original blueprint. Wanted $15K to start, didn't even hear/see the system run. Wanted to install boiler feed system, never mind the print showed this was a low pressure, gravity return system before the boiler was replaced. The receiver is not required, but helps deal with the near-boiler piping.

    We're restoring an old historic home and ran into some issues which put us over budget. I've been able to figure out the bad decisions/repairs the previous owners were subject to. Even if I had the money, it doesn't "feel right" to pay someone $15K to get my system back where it should be. Being familiar with auto-related sites, I found the wall and it's been a big help, along with Dan's books.

    So, I've rebuilt the F&T's, installed an additional one at the end of the second main, moved the main vent from it's end-of-main-destroyed-in-one-week location, replaced all the radiator traps (previous companies had simply removed them), installed a vaporstat, etc., etc. I'm in the final stages of getting the system where it needs to be, and appreciate the help of the Wall.

    If you know of any pro in Indianapolis I'd welcome the referral.

    BTW I re-read some old posts and Steam Problems and focused on the water leg I have in my receiver. I added a main vent to the outlet of an F&T in the boiler room (don't need one there but example of 'guessing' by previous contractors and handy location for vent). Still one or two knocks but lots of air coming out of that vent and *much* better startup. Condensate moving to receiver much more quickly - does that make sense?

    THANK YOU and your fellow posters for the time you spend answering question on this board.

    Brian in Indy
  • jerry scharf_2
    jerry scharf_2 Member Posts: 414
    Only 1 state away


    It wouldn't be free, but you live one state away from a very fine steam person who frequents the wall. Dave "Boilerpro" Bunnell, located in Amboy, IL is a great guy who you might be able to entice to look at your system. You can search for boilerpro to get contact information.

  • brian_27
    brian_27 Member Posts: 7

    Not looking for free, just savvy - thanks for the rec, it's over four hours away but I'll shoot him an email anyway -

This discussion has been closed.