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Are there things that should be done after replacing return piping?

Jim_NY Member Posts: 43
edited November 2021 in Strictly Steam
A section of a basement-floor horizontal steam return black pipe (that had apparently had gotten buried by moist dirt) rotted through and is leaking. Plumber proposed also replacing adjoining vertical and horizontal pipes totaling ~25ft (after first suggesting re-doing the entire 75 foot run through walls, staircases etc.).

For example, wondering if there should be some sort of boiler or pipe cleaning etc.


  • mattmia2
    mattmia2 Member Posts: 8,372
    You will need to skim the boiler to get rid of the oils from that new piping.
  • Jim_NY
    Jim_NY Member Posts: 43
    I'll have to ask if that's included in their proposal.
  • Jamie Hall
    Jamie Hall Member Posts: 21,512
    But there's no need to replace any of the vertical lines. For that matter, if you replace the wet return in copper -- which is quite permissible -- even skimming becomes sort of a non-event.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • Jim_NY
    Jim_NY Member Posts: 43
    edited November 2021
    Was hoping just the one pipe could be swapped, but the proposal says "1 1/4" black pipe", from the ell or tee or (?) with the clogged air vent from my last post here (photo below) being replaced, vertically down which then turns 90 deg ell(?) to the failed horizontal pipe, ell(?) to the next horizontal pipe, which connects by a union(?) to a long in-the-wall horizontal pipe (which is not to be replaced).
    Understand that at the other end of the basement the (easy-to-get to) horizontal wet return had been entirely replaced about 30+ yrs back, and would describe it as yellow-red-brown, though lately with blue-green tinges. Sounds like at least a copper containing metal.

    Pic from the old air-vent post.
    EBEBRATT-Ed Member Posts: 13,759

    The only piping that usually rots is the pipe below the boiler water line either horizontal or vertical.

    However to avoid having to thread pipe in place which may or may not be an issue (depends on location) a little more may be changed to get back to the next fitting
  • Jim_NY
    Jim_NY Member Posts: 43
    edited November 2021
    Interesting, thanks. So more corrosion where water stays in the lines all the time, all seasons, rather than where (hotter, but hopefully "dry") steam passes during heating season.
    Now curious if such pipe (which looks horrible where it's leaking) usually shows signs of distress on the outside before failing, or if it usually happens internally out of view.

    As far as the scope of the replacement, I'm certainly not qualified to second-guess best pipe fitting practices.
    EBEBRATT-Ed Member Posts: 13,759

    The pipe can rot from the outside or inside.

    Steam piping in general lasts forever. You can cut into a 120 year old steam line and it is generally as good as new.

    Condensate piping below the water lines rot because condensate can be slightly acidic which would attack the inside. Also any sludge inside the pipe tends to make it rot from the inside overtime.

    If the pipe is buried in the dirt or in concrete it can rot from the outside as well dut to moisture the lime in the concrete etc.

    But generally even in an abused residential system the pipe will usually last at least 20-30 years

  • Jim_NY
    Jim_NY Member Posts: 43
    What an extensive topic!

    Your earlier response prompted a casual search for corrosion pics. When the moist dirt was moved to look at the leak, think perhaps the surface of the pipe looked closer to photos that (at a site called corrosionpedia) were labeled deposit corrosion and microbiologically influenced corrosion.
  • cross_skier
    cross_skier Member Posts: 201
    I have 65' feet of 1-1/4' galvanized wet return that was installed above ground and insulated 23 years ago.  It is doing fine at least in the area where water is fed into the system about 15 feet from the boiler.  Only one data point but I thought it was worth sharing since galvanized is frowned upon by many.
  • ethicalpaul
    ethicalpaul Member Posts: 4,804
    IMO galvanized is no harm in a wet return. I'm not sure there's even a harm for steam...I think it's frowned upon strictly because it's unnecessary and more cost, but I could be corrected.
    1 pipe Peerless 63-03L in Cedar Grove, NJ, coal > oil > NG
    JUGHNE Member Posts: 10,779
    I have read that steam will flake off the galvanizing and create problems in air vents and seal/seats in maybe traps.

    I have a good assortment of galv fittings, I will use them for wet drains on blow downs etc.

    They really stand out like the proverbial tvrd in a punchbowl though.
  • Hap_Hazzard
    Hap_Hazzard Member Posts: 2,826
    Wet return piping tends to fail first near the joints because the threads cut almost halfway through the wall of the pipe. Using copper is a good idea because it's less prone to corrosion. Stainless would be great if you could afford it.
    Just another DIYer | King of Prussia, PA
    1983(?) Peerless G-561-W-S | 3" drop header, CG400-1090, VXT-24