There's a leak somewhere around my circulator pump and the fittings that connect it to the Weil McLain CG-5 gas boiler have corroded and should probably be replaced. (right?)

Not very familiar with these fittings. The pump is a Bell & Gosset Little Red Pump and looks like 1" copper connects to top of pump and then the fittings on the bottom connect to the boiler which looks like 1" too then a drain valve.

As best as I can guess there's a Tee fitting (1" x 1" x 3/4") made of iron based on what the corrosion looks like. Then a drain valve. Only thing I can find that looks similar is a black iron fitting but it doesn't seem to be for water applications. http://www.homedepot.com/p/LDR-Industries-1-in-x-1-in-x-3-4-in-Black-Iron-FPT-x-FPT-Reducing-Tee-310-RT-1134/100577900

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What should I be replacing all that with and what materials? Looks like I'll need a reducing tee, drain fitting and the flanges for the pump. And probably a new pump.

Also, will the pipe leading the the boiler need to be replaced due to the corrosion and is that something that can even be replaced?

Here are some pictures.

enter image description here enter image description here

Here's a picture of a different model Weil McLain boiler that that has the same drain and Tee fitting. It's the black fitting over the drain on the side.

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  • Some clearer pictures would really help. There appears to be quite a bit of corrosion, so you might consider removing as much existing plumbing as you can, then redoing it with copper/brass or PEX. Also, pipe sizes rarely correspond to their nominal dimension (ex. 3/4" NPT has an OD of 1.050"), so without a proper measurement, it might be difficult to determine exactly what's going on. – Hari Ganti Mar 16 '17 at 19:30
  • @HariGanti It's hard to get a clear picture in that location. I found another WM boiler that has that same fitting as can be seen in the new picture I uploaded. Seems to come with some boilers so I contacted WM to see if they can help. Hoping someone knows exactly what it's called and what material because I'm having a hard time finding it on parts sites. – OrganicLawnDIY Mar 16 '17 at 20:23
  • The manufacturer may know the details, as you said. The picture you uploaded, however, only really tells me that they use soldered copper pipes (from what I can see). Beyond that, a generic picture doesn't really help. You need to find out what you have (because it looked like there was galvanized back there, or black pipe with lots of dust). Your materials and sizes may vary. – Hari Ganti Mar 16 '17 at 21:32
  • Stop the leaks. It's unlikely that the corrosion on fittings is enough to warrant replacement, and it will stop when the leaks stop. – Ecnerwal Mar 17 '17 at 3:45
  • @Ecnerwal it looks like it's the pump housing (not from the flanges) that's leaking. No leaks from top flange, and top of bottom flange is wet as well as parts around the pump. I'm not sure if that can be repaired. The pump is over 10 years old. Figured I'd have to replace the pump. Once I'm spending $200 for a pump another $20 or so for the other fittings seems like it's worth the money. Going to replace everything from the pump down to the drain valve. Might keep the top flange and hopefully the nipple that leads into the boiler but will have them on hand. – OrganicLawnDIY Mar 17 '17 at 4:15

If you can measure the outside diameter of the copper pipe above the pump and subtract 1/8" from that dimension (diameter) you will have the size of the copper pipe.

Then, the pipe at the bottom of the pump and into the boiler should be the same size but is black iron pipe schedule 40. Schedule 40 is standard weight pipe, the same as used for gas lines. Sometimes, the pipe into the boiler is one size smaller than the rest of the pipe, for some unknown reason especially if this an old boiler.( It was just how the boiler companies piped it).

If the system works and heats OK, I would buy the same size pump which usually comes with flanges and gaskets that fit the pipe size used. Today, the flanges and gasket set may come as a separate item depending on where you buy the pump.

The fitting below the pump looks to be standard black iron. You can buy either a reducing tee to accept a 1/2" or 3/4" boiler drain valve or a cheaper way may be to buy a standard tee and a reducer to fit the valve. Regular black iron fittings sold by Lowe's and Home Depot can be used on hot water boilers. They don't have to be a special material. Don't let anyone tell you that you need a special fitting of brass, galvanized, stainless steel or something. Boiler water is usually not corrosive.

Once you take the piping apart in the spring you will be able to better know the sizes of the piping and it's condition. As for the pipe going into the boiler, if it needs replaced, be careful when taking it out. If it breaks you will need someone who knows how to take out the broken piece. From the picture the pipe into the boiler looks like 1-1/4". You can "google " (standard pipe dimensions) to find the outside diameter of the steel piping.

Asker Edits: This was a very helpful answer to find what I needed and the pipe sizes. After I used the advice above to figure out what I needed I finally found the manual online (totally forgetting the paper manual I have near the boiler) so included a diagram and the parts so I can accept this answer in case anyone in the future needs this info for a Weil-McLain CG boiler.

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From bottom up:

  • 1) 3/4" Drain boiler drain valve
  • 2) 1-1/4" x 3/4" x 1-1/4" black iron tee (3/4" at bottom)
  • 3) black iron nipple. 1-1/4" diameter. 5-1/2" length for Taco 007 circulator pump, 6" for Bell & Gosset little red pump (LR20 1/20HP), 5" for B&G100 or Taco 110
  • 4) 1-1/4" black nipple close
  • 10) bottom flange 1-1/4"
  • 9) top flange 1-1/4" or different depending on size of pipe above
  • 13) Pump gasket (came with pump)
  • 6, 11 & 5) Bolts and Nuts 7/16-14 nut, 7-1/15x14x1-1/2" bolts. 4 nuts and bolts come in a pack from the pump manufacturer or can be bought at big box store in a pack with the flat style flange gaskets.
  • Awesome answer and most of what I was looking for especially in terms of material. Do I use pipe dope for the fittings? Found the model number. Any chance you happen to know what size the reducing fitting would be for a CG-5 boiler? Might have to do it sooner than later as it's leaking quite a bit. Hopefully it doesn't all fall apart and I have no heat. – OrganicLawnDIY Mar 16 '17 at 21:21
  • I do not know the size of the reducing fitting. They change with every boiler mfg. and series of boiler. If I were to guess the tee fitting would be a 1"x3/4"x1". I have installed and serviced both steam and hot water boilers and connected piping for 40 years until my retirement. As for the type of pipe dope, that changes with every tradesman out there. Myself , I choose teflon tape covered with pipe dope; (2-3 wraps of tape and a coating of any cheap dope, not the shellac type. Or you can just use RTV silicone in the color of your choosing. No RTV silicone on the pump flange gaskets. – d.george Mar 17 '17 at 9:58
  • Good luck with the Kitchen remodel. What type rads are in the rest of the house? I like these old systems. The old time installers usually did things correctly with no short cuts. Adding Danfoss valves and thermostats give better temperature control in all rooms. – d.george Mar 17 '17 at 10:16
  • rest of the house are in-wall cast iron radiators. Not doing a kitchen remodel was just going to add the kick space heater but that might have to wait now as fixing the leaking pump is a priority and the feeder valve needed to be replaced too.One more question. Do I use pipe dope for the T-fitting and related connections? – OrganicLawnDIY Mar 17 '17 at 16:03
  • The Tee fitting and drain valve and bottom flange were too corroded to deal with but after some of the rust flaked off they seemed sound so followed @Ecnerwal advice to leave them be. The lower pump bolts took a while to break free so I cut the plan down to get heat tonight. Replaced the pump, bolts, pressure regulator, shut off valve and an elbow that was leaking. Noticed a very small weeping leak on top of the top flange. Will fix that in the spring when I put kickspace heater in. I was previously loosing 5qts over night, now it evaporates before it drips so I bought some time. Thanks again. – OrganicLawnDIY Mar 19 '17 at 4:53

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