Click here to Find a Contractor in your area.
Welcome! Here are the website rules, as well as some tips for using this forum.

If you've found help here, check back in to let us know how everything worked out.
It's a great way to thank those who helped you.
Need to contact us? Visit

Weil mclain boiler section replacement

rschepsrscheps Posts: 4Member
Are there any work instructions out there for replacement of an intermediate section in a well McClain CG hot water boiler? I replaced a cracked intermediate section in my boiler and all was happy and dry for 2 years. Then the joints started leaking. I used all new square cut o rings and the right high temp silicone on the flanges between all the sections and on the o rings. it only held for 2 years so I must have done something wrong. Tie rod torque Wrong perhaps? Silicone on O rings or not?. Any advice?


  • FredFred Posts: 8,277Member
    Are you sure the leak is at the joints? Once a section gives out on a boiler, other sections typically aren't far behind.
  • rschepsrscheps Posts: 4Member
    Not 100% sure it is the joints. But it is leaking from the side with the water channels and orings. When the section failed before it cracked right on the bottom closest to the burners. Maybe I should consider myself lucky that it gave me 2 more winters of service after the first cracked section
  • ChrisJChrisJ Posts: 10,500Member
    Why did it crack the first time? That's not normal.
    Single pipe quasi-vapor system. Typical operating pressure 0.14 - 0.43 oz. EcoSteam ES-20 Advanced Control for Residential Steam boilers. Rectorseal Steamaster water treatment
  • HVACNUTHVACNUT Posts: 2,855Member
    How old is the CG? Is there still a block warranty? If not I dont know how many times I'd keep replacing sections. Seems a little redundant. Commercial boiler, ok. Residential, not so much.
  • rschepsrscheps Posts: 4Member
    25 yrs old, so way out of warranty. We had a leak in a baseboard overnight 2 yrs ago that may have drained the system and caused it to dry fire before we discovered the leak. There was no LWCO at the time.
  • Jamie HallJamie Hall Posts: 12,132Member
    It really shouldn't have needed any sealant. One hopes that the RTV didn't interfere with pulling the sections together enough to get the O-rings to do their job -- they can and will eventually leak if they aren't fully seated properly. However, what's done is done. As @Fred said, though, once one section cracks (or rusts through!) the others may not be far behind, an whatever stressed it enough to crack the one may well have created an incipient crack elsewhere which just took time to grow.
    Br. Jamie, osb

    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England.

    Hoffman Equipped System (all original except boiler), Weil-Mclain 580, 2.75 gph Carlin, Vapourstat 0.5 -- 6.0 ounces per square inch
  • EBEBRATT-EdEBEBRATT-Ed Posts: 6,553Member

    download the boiler manual and follow the instructions. 25 years may not be worth the effort.
  • rschepsrscheps Posts: 4Member
    Thanks all
Sign In or Register to comment.


It looks like you're new here. If you want to get involved, click one of these buttons!