Replacing corroded class 250 or 300 black/malleable iron pipe & elbow on WGO-4 series 3

masscat

Hi all, I need to replace, what appears to be, a heavily corroded class 250 or 300 malleable iron elbow and section of 4ft, 1-1/4" black pipe near the return of my Weil-McClain P-WGO-4 series 3.

1. Can I use class 150 fittings/pipe? I can't easily find class 250 or 300. The manual doesn't seem to specify. Looking at an Anvil cut sheet suggests I can go up to a temp of 250F at 225PSI with class 150 fittings. The max temp I've observed on my heat gun exiting the boiler is ~190F, but I know the boiler is firing above 370F.
2. The manual suggests front section B1 return piping has a 1-1/2" pipe size. My system looks like it immediately reduces to 1-1/4" at the return with a bushing (all the pipes measure 5-3/8" circumference…~1.71" diameter.
3. I'm getting some used Ridgid tools (die head, ratchet, reamer, 3-wheel cutter, pipe stand). I'll have a retired machinist (dad) who installed/maintained his own boiler helping, but he prefer sawzall and hasn't done this in years.
4. Any watchouts for draining the system?

See images below.

pecmsg

those look like schedule 80 fittings. There used on high pressure systems.
I don’t think you need something that heavy on a domestic boiler.
I hope there’s a union nearby!

mattmia2

if this is hot water you can replace it with pretty much any black fittings and pipe or you could also replace it with copper.

masscat

https://forum.heatinghelp.com/discussion/comment/1895944#Comment_1895944

Baseboard heat. Indirect HW is on the other side.

EBEBRATT-Ed

You can certainly use 150# malleable or 125# CI fittings. They are the same dimensions as the 250 or 300# fittings.

As mentioned above copper is a good choice as well

hot_rod

a sawzall, handheld power threader, union and some new fittings is the fix.