replacing taco mixing valve and purging

crabbydad

Taco mixing valve on my radiant heating is leaking and i am going to replace. My system has 5 zones, they all have a hose bib to use for draining,purging except for this one. My thought was to close off all the valve for the other zones and drain this one down using the drain at the bottom of the boiler, being careful to drain to just below the mixing valve so i don't drain the water from the boiler and the common return line. I will then purge this zone using the drain at the boiler. I figure i will have to purge all zones since i can't really isolate this zone. Does this sound like the best way to do this? After posting i realized this forum was titled radiant professionals, so should i repost in another forum.?

rick in Alaska

I would try shutting off the three valves around the mixing valve. Then put a bucket under the mixing valve and loosen the nut on the top of it. If the pump has a built in check valve, there is a good possibility it might only drain a little and then stop. If it doesn't, then you might have to go with the drain down you described.
Unfortunately, that mixer is notorious for leaking around the stem.
Rick

crabbydad

i was thinking the same thing, since the valve leaks when i open it all the way, i was going to let it drain down slowly. I also posted this question on the main wall and had a good suggestion to install an isolation purge valve at the same time. I was thinking of doing that, then i could purge there when i was done