possilbe to drain 1 zone without having shut-off valves both into and out of boiler?

[rxdork]

I need to drain and temporarily disconnect 1 zone of 3 for a basement remodel. I have a shut-off valve going to boiler on each loop and a drain above each one. There isn't a shut off valve leaving the boiler, only flo control valves. I don't think I can use them to stop water flow and I believe if I start to drain 1 zone it will pull water from the whole system. I need to have other zones working for heat. Is there a way to drain and disconnect 1 zone without having to add another shut off valve leaving the boiler?

[mtcummins]

I'm not positive, hopefully someone else will have more experience than I do...

But I think you can drain one zone by shutting off all zones, then opening the drain and the plug in the bottom of the control valve. This should let water drain out of that zone, the other 2 control valves/shutoff valves should stop it from backflowing out of those zones. You'll only lose a little out of the boiler side b/c of the riser right before the zone breakdowns, unless you get a crazy siphon going, but I think having both of those locations open on the zone you're draining will stop a major siphon from occurring.

Be sure to turn off the boiler and the feeder first, and have a plan for how you're going to close off the control valve end of the system so you can get it done quickly and get your system up and running again. If it happens to be the zone with the union, that would make things easier...

[mtcummins]

is there no expansion tank in your system, or is it located elsewhere? I'd usually expect to see it below the air separator/feed valve.

[rxdork]

I need to drain and disconnect zone for remodel work which could be few weeks. I will be hooking it up after work done but still need heat in other zones during work. Sorry wasn't clear on time it would be disconnected. Is adding another water shut off my only option?
And there is an expansion tank located out of frame. Its mounted to left in picture of flo control valves between ceiling rafters

[mtcummins]

What I said above assumed you were going to have it shut down for a while. You have to figure out how to close off the boiler end of the loop your disconnecting, or you'll have weird air problems in the rest of the system. If its the union branch, you can use that union to put in a stop of some sort, and the valve at return end, then pressurize the system and run it. Also, since you're draining it, I'm assuming you're cutting into the piping, so you'll have to have the supply side of that zone sealed off somewhere to do that.

If it were me, I'd just bite the bullet and add the valve to that zone at least. It'll make life easier if something is needed later.

[johnjh2o1]

You need a valve on the supply for each zone to be able to drain just the one, which you don't have.

John