bleeding a boiler system

big fred

I m not sure if the system has to be off or on when getting started

Scuba_Dave

Radiators ?
I have a hot water boiler system
I turn the heat down & then bleed the radiators

Plumber101

Turn the gas off to the boiler and make a call for heat then bleed away

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sdsester

Bleeding the boiler of sludge and stuff or bleeding the system of trapped air? You probably need to tap the radiators of it is an air problem and I think the system needs to be one for that. Be careful though, don't get burned by the steam!

I find it handy to have a short garden hose ready and going to a drain, laundry sink, or whatever when flushing out boilers. Beats hauling buckets of disgusting crud. Do make sure the valve closes again all the way when you are done. Sometimes crap will get stuck if it is not flushed out all the way.

Bob Mariani

This depends on if you have valves available to isolate the boiler from the zones. If you do then you can close these off after turning the gas or oil off to the unit. Then backfeed water into the unit and bleed out the air using the drain spigot. If you do not have this setup then you need to run the circulator in order to force water through the system to extract air. Bleed one zone at a time by closing all valves and only opening the two for the zone you are working on. Turn the thermostat to the highest setting to get the pump running.