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Mouat system boiler replacement

Danny_Jr Member Posts: 14
Quoting a job to replace a modern boiler with small steam chest with another modern boiler. The piping for the system has a return reservoir. I'm thinking it was added when they replaced the original boiler. The reservoir receives the drops from 4 vented dry returns and a Trane #411 Indirect Return trap. The reservoir is leaking as well as the boiler and the top of the return trap.  I really don't want to rebuild the reservoir or add a boiler feed if it is not necessary. Planning on installing the Hydro Level VXT feeder & #400 LWCO. Using a vapor stat and compound gauge.

This is a two pipe Mouat Vapor system with both their valves and radiator traps. I failed to notice whether their was a standard pressuretrol or a vapor stat.

Two questions: The boiler is rated for 113 pounds an hour. Do I need the reservoir or feed pump. Weil McLain has a drawing of how they would want the reservoir installed on their steam system. They use 8" pipe the length based on the boiler capacity.

The other question is what to do regarding the Return Trap? With the end of the main vented and if I can make the "B" dimension do I even need one?

Attached photo shows how they tied the steam supply into a vertical header of 6" down to the reservoir below with more 6" installed horizontally to receive all the return drops.


Dan Wood Jr.

Remember, when you find yourself between a rock and a hard spot, that's where diamonds are made!


  • JStar
    JStar Member Posts: 2,752

    I shy away from unneccessary parts, like resevoir tanks. However, it may become neccessary if the condensate produced by the radiators is more than the boiler and returns can hold. I wwould personally install the new boiler without a tank, but add a clause that it may be needed in the future.

    There's no need to remove the old Direct Return Trap. Just leave it there for somebody else to enjoy in 100 years. It's a cool part of heating history. You can see a job we did on a Trane Vapor system with a similar Return Trap. We installed a new sight glass on it for historical integrity.