Weil McLain Plus 80 indirect water tank

hunnypuppy

I have a W/M plus 80 indirect hot water tank connected to my Weil McLain boiler oil furnace.

Could someone please help me understand 2 things:

1. There’s an auto air vent on top of the hot water tank which is leaking and I want to replace it. Is that connected to the boiler line (12 psi) or is it connected to the domestic water (60 psi)?
2. The manual https://www.weil-mclain.com/wp-content/uploads/indirect-fired-water-heater-manual_1.pdf says that the inner tank is domestic water and the outer tank is the boiler water on Page 16. Traditional diagrams of an indirect water heater show a coil running from bottom to top along the center of the tank which carries the hot water from the boiler (shown as an inner tank/coil) and which then that heats the domestic water surrounding it. (Outer tank). But the way the manual describes it doesn’t sound anything like that but the reverse, the hot boiler water surrounds the domestic water tank. Could someone please help me understand what the internal of this water tank looks like.
   

Karl Reynolds

What you have there is a Triangle Tube Smart Series tank within a tank indirect water heater branded by Weil Mc Lain. The domestic water is in the inner tank and the boiler water surrounds it in the outer tank. Best design in my mind and my 60-gallon model is twenty-four years old. You could replace the air vent with the Triangle part number P3KITAV02 or a Taco 4004.

HVACNUT

https://forum.heatinghelp.com/discussion/201897/weil-mclain-plus-80-indirect-water-tank

If I remember right, its a full 3/4" Hy-Vent.

If there are isolation valves on both the supply and return for the water heater, you can close them, then open the purge valve (with hose and bucket) for that loop to drop the pressure to 0 psi.

You don't need to order from Triangle Tube, you can use SupplyHouse and look for a Taco 3/4 Hy-Vent.

Just making sure. You have a bladder type expansion tank, correct? Not a compression tank in the ceiling.

hot_rod

I thought those vents were 1/2”

Regardless you could increase or decrease the pipe size if you get the wrong one

Intplm.

@hunnypuppy

If you don't want to wait for the vent to be changed, you can tighten the cap finger-tight. It's similar to a bicycle valve.

EBEBRATT-Ed

The vent is on the Boiler water not the domestic correct?

HVACNUT

https://forum.heatinghelp.com/discussion/comment/1862269#Comment_1862269

Yes, on the boiler side.

JimP

It’s 1/2” female npt. Last time I bought one Triagle Tube had changed and provided a manual vent. I believe that leaking auto vents had damaged too many heaters since the outside tank can rust. I like the auto vents but they require maintenance. You can go either way.

hunnypuppy

this is the vent. It appears to be a 1/4 mounted on a 1/2 adapter.

So this is on the boiler side, I just need to shut off the isolation valves on the boiler side, drain the water a few drops to relieve the pressure and then unscrew and replace right?

hot_rod

this model comes with a safety cap to stop a drip if the vent fails

Ideally if you have a good air purger in the system that auto vent works for the first filling. Or if you drain and refill

If air comes out on a regular basis, somehow air is getting in to the system?

If air is entering somehow, that will cause a lot of rust and corrosion, that is a plain steel tank

Intplm.

https://forum.heatinghelp.com/discussion/comment/1862317#Comment_1862317

Yes. And, I see, most likely, a half-inch by eighth-inch bushing under the vent. I would be ready to change it with both sizes, just in case something breaks.