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Looking for help/advice fixing a SAF-T VENT system

Johnbo Member Posts: 6

First off, I'm a homeowner, but a reasonably handy one (I think!). About 20 years ago (approximately), my local propane company converted my radiant baseboard system from an old worn out oil burner to a Weil-McLain GV6. A number of mistakes were made in this process, but these are fodder for another post. When the boiler was first installed, it was vented with a translucent plastic pipe. About a year afterwards, I was contacted (not sure by who) and the plastic stuff was removed and replaced with 3" SAF-T VENT, at no cost to me.

The exhaust system parallels the intake piping, which is in 3" PVC. The exhaust comes out of the side of the boiler, does a 90, then straight up for 4', the does a 45 bend and runs to near the ceiling, another 45 and runs nearly flat for about 16'. (I believe that it is minimally pitched back to the boiler.) This was the old style SAF-T Vent that required the special red RTV to assemble the system.

So, the problem is that the Weil McLain adapter that fastens to the face of the CI block and turns 90 and has the drain nipple on it has failed. The drain nipple had 3 tiny tack welds to hold it to the rest of the part. (I seriously doubt that this was gas tight). I started seeing a lot of water on the floor and the nipple broke off when I touched the flexible drain hose. Over the last couple of years, I tried a number of 'fixes' with high temp silicon, pieces of stainless wire to mechanically afix the nipple to the fitting. The first thing that I did was buy (and install) a CO detector in the room with the boiler. The attempted hacks are not permanent by any means and judging by the water on the ground under that spot, not water/gas tight.

I believe that when the plastic vent was removed, they left the original adapter on the boiler. But, in stroke of good luck, they left me with a replacement adapter (with a much better weld) that came with the refit kit from Weil-McLain.

The problem is that I can not figure out how to get the existing adapter loose from the SAF-T Vent piping. That RTV is strong stuff and I've tried to poke a knife blade into the gap between the outer portion of the adapter and the SAF-T Vent pipe (which is actually a SAF-T Vent 73WMSTRT adapter). But, the access to this location is really poor and I can't get to all sides. I'm pretty sure that I could get the adapter off of the front of the boiler, once the other end is loose. I've not found any magic solvents that would appear to work (but, I've not tried them). I'm a bit nervous about getting this thing halfway apart and finding out that I've damaged something irreplaceable or I can't get it back together.

I've thought of sawing the SAF-T Vent starter off and trying to disconnect this from the next piece of SAF-T Vent, but again the clearances are tight. I'm worried that my old mangled up pieces of SAF-T Vent would not seal well with the newer gasketed versions. I can't find any reference on the HeatFab web site about using the new 93 series stuff with the older 73 series that I have. I suppose one approach is to complete scrap all of the existing old SAF-T Vent stuff and start over. This feels rather expensive.

Is there a better approach to this? Hydronic heat is a bit rare in my rural area, so finding someone with experience has been problematic. In the past, when I had replumb the system to fix some of the conversion issues, I found a design shop that did a redesign and sold me the parts while I did all of the piping and installation.

Thank you for reading to the end of this very long post and I look forward to your comments.


John D. Bowne
Cornelius, OR


    HVACNUT Member Posts: 4,195
    Weil McLain tech support
    1-800-526-6636 might offer assistance. Make sure you have model and (CP)serial numbers.
    They're only supposed to deal with industry techs, but maybe they can help. You might wind up replacing the venting completely.
  • j a_2
    j a_2 Member Posts: 1,796
    Post a picture....Companies that sell fuel should just sell fuel....jmo
  • Johnbo
    Johnbo Member Posts: 6
    Completely agree about not using a fuel company to make design decisions. The root of all of my problems over the last 20-ish years, is that the boiler was way oversized. My home is 3400 sq ft, but half is rarely used and I live in a "once in a while we get snow" zone. The oil burner was rated for 90K input BTU (but probably 50-60% efficient), and they didn't want to have a lack of heat, so I have a 120K input BTU with something like 90% efficiency. The water heater tank in the back is my attempt at increasing the thermal mass of the system. But, even with that it rarely runs for more that 1-2 minutes, then off for 5-10 minutes, once up to temp and all zones flowing. Output temperature is set to about 210 degrees with as low of kick in temperature as possible (leftover from my attempt to get as much heat away from the boiler). All zones are SlantFin radiant baseboards, all in 3/4" Cu or Pex-Al-Pex.

    Pictures as requested. I'm not sure whether to be proud or embarrassed by what I created. The design was from a residential design/build firm a few years after the boiler was installed and I started to realize that the rapid cycling was not normal. The layout was mine to fit the space.

    First the general layout.

    Now, the exhaust vent and a look inside at the bodge job.

    I'll give Weil McLain a call. Anyone have a way to get in touch with HeatLab? I've filled out a web request form, but haven't heard anything from them in a week or more.


  • Zman
    Zman Member Posts: 6,989
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • Johnbo
    Johnbo Member Posts: 6
    I don't believe that I've seen these instructions before. I've seen that Tee in the HeatFab web site, but wasn't sure what it was used for. The 90 adapter that I have (1 installed/broken, 1 uninstalled/good) goes from the boiler block to the outer face of the sheet metal enclosure for the boiler. I'm pretty sure that this is a Weil-McLain part. There is a SAF-T Vent part 73WMSTRT part that goes from the side of the boiler (the outer end of my adapter) and connects to the SAF-T Vent fittings.

    My assumption was that the nipple in the WM adapter was to pick up the condensate from the entire vent stack.

    If I was to use the described Tee, where does the condensate line go? The pictures make it appear to go to an additional fitting on the side of the boiler. I have only one fitting and that is supposed to go to the condensate pump (no drain in the area). I would assume that this needs to have some sort of a P-trap loop in it to keep the exhaust from escaping.


  • Johnbo
    Johnbo Member Posts: 6
    I think that the difference in the tees is due to the age of the boiler. From what I can see in the drawings from the WM parts catalog, I have a Series 1 or 2 boiler, while the referenced document is referring to a Series 3 or 4. The structure of the exhaust port on the bottom of the boiler is quite different between the two generations.

    Anyone ever had to remove and replace this adapter from the CI block? I'm a bit worried about removal of that one screw that holds the adapter on. (Plus a lot of RTV)


  • hot_rod
    hot_rod Member Posts: 15,033
    If you successfully get the mounting screw out the adapter should break loose from the RTV seal. A very large channel lock pliers can be used to put some twist on it as you pull.

    I have heated those seals with a torch also, not sure that is an approved method :)

    I think the early versions used that ell, I had a early, 1994 version with that ell. The tee would need to go on with a straight section, then turn up.

    The tee has a better dished out section to collect condensate. As I remember the ell just had a stub welded in, not an ideal "catch" zone.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Johnbo
    Johnbo Member Posts: 6
    I'm a bit nervous about getting the screw out. Are these typically Locktite-ed into place?

    I'm hoping that the RTV didn't get into the threads, but realistically, with the way the RTV was applied, it would have been hard not to do.


  • unclejohn
    unclejohn Member Posts: 1,749
    You are opening a big can of worms if you try and get the bolt out that holds the 90 in place. If it is only leaking at the drain nipple I would go back to square on and re do the repair. Clean good and dry it up with a hair dryer and get lots of silicone.
    JUGHNE Member Posts: 8,949
    I installed a GV-4 in my new house in 1995 with the plastic H&C vent system. Changed out under the SS program later.

    I have since changed to a Mod-Con. So with no worries as the new boiler was running I removed the 90 from the CI horn of the GV-4.
    The screw came out OK.....maybe did the old trick of slightly tighten first before removing. Just have the correct screw driver size, and not a cheapie...I think it is Phillips sure it fits correctly.
    IIRC it is a SS screw screwed into CI. Clean the silicone/RTV out of the screw head first to avoid roll out/slippage.

    The RTV joints gave up pretty easy with twisting. Maybe gripper gloves or the jar lid gripper pads.
    The new SS kit at that time included a drain for the horizontal line to be installed just before rim joist penetration.
    There was no drain tee outside of the boiler, just on the inside elbow. (All the drains must be trapped BTW)

    With this removed I could see that part of the CI discharge horn had corroded away but enough was left to get a good seal. This apparently was caused by the internal mix valve T-stat failure which was a common failure in GV's. It allowed for low temp return water to cause condensation in the boiler.
    There is a fix for this problem if you have it also.

    The old GV sits in the basement and is for sale ;)