Webster Modulation Vent Trap

Christian Egli_2

I find it strange that your Webster modulating vent trap is holding back your liquid condensate because that's not what the gadget does on any ordinary day.

It does not interfere in the condensate flow back to the boiler, it only acts to stop the liquid from spilling out of your main air vent, which is the open hole on top of the modulating trap (which may have an optional vacuum check valve).

There are only two failure modes:

First, if the modulating trap remains shut, no air will be able to escape your system. With radiators air bound, you won't get steam. To dislodge the float mechanism and re-open the air hole, try hitting the trap body gently, otherwise a tear open and clean up will help.

Second, if the trap remains open, you might experience a water discharge from the air vent, but you wouldn't have an air bound system either. Again, a clean out will solve everything.

Thirdly, there probably isn't anything wrong at all with the trap. The fact your returns might be flooding is because the boiler pressure is too high and there isn't enough stacking height for condensate to squeeze back in where the action is.

How high a pressure do you have? Do you have a vaporstat?

Or, all your symptoms may simply be related to condensate return lines sclerosis. With years of rust and dirt accumulating inside the returns and maybe some sagging along the way your pipes no longer have the capacity to channel the condensate. New return lines might be what you need.

Lastly, are all your radiator traps in perfect functioning order? If just one is leaking steam into the returns, this could cause the blockage you suspect.

Tell us what you discovered and what you are being told, but remember, the Webster modulating vent trap is nothing but a gigantic name for a simple float air vent common to all hot water heating system, but somewhat unusual to steam systems. And if steam is coming out of the vent trap, don't blame it, it isn't supposed to close on hot steam (no thermostatic component here), go hunt for the faulty thermostatic radiator steam trap.

Keep warm.

Laura & Tim

Repair? Replace?

We have a two-pipe steam system powered by a Bryant Heater Company Tubular Gas Boiler (Boiler No. 3-443 Serial No. 309801)with patents ranging from 1921-1936.

The system uses a Webster Modulation Vent Trap which has stopped working and is causing the system to back up (so no steam gets to the radiators...so no heat in the house).

Does anyone have any recommendations on how to repair or replace this type of vent trap?

Thanks.