Proper way to bleed/flush a 2 zone split loop

nemerrill

Hello all and thanks in advance for your help!

This is my first time working with balancing valves, backflow preventers, etc. Despite bleeding all the bleeders on the baseboards and the wall unit, the system had extensive gurgling all last winter. After drawing out the system I think I have the theory somewhat under control: close the ball valves (left of pumps in the drawing) on both zones, open the spigots (left of the ball valves) and let the water flow (while tapping baseboards) til the bubbles stop. Problem is that the pressure (15-25 psi) drops quickly and takes a long time to come back up. flipping the switch on the pressure regulator on the supply line does nothing. Could there be a holdup in the supply line? bad regulator? I have done this before on single loop systems and the regulator allowed for much greater flow when flushing.

Please note that there are several more parallel loops not included in the drawing.

Lots more questions for whoever wants to answer:

-valve on expansion tank was hissing. Should i replace valve core? reset the precharge pressure? This means i need to release all water pressure and pump with air to the 12 psi precharge as stated on the label?

-balancing valves show clear signs of serious corrosion and leaking (eg the tuna cans hanging to collect the drips, though i havent noticed any drips). sweat on new ones? Remove the cores and try to replace o-rings? let sleeping dogs lie til spring?

-some hack used 8' of red pex. i would need to cut open the wall to replace…how necessary?

-bleed the bleeders with the circulator pumps on or off?

THANKS AGAIN

Big Ed_4

You can bleed all zones from the boiler .. The shut off on each return then drain off from the spigot up steam .. The parallel system you will need to shut off the other two…

Jamie Hall

You may find that you need to really purge each line of pipe individually, and you may not have the valves to do that easily (if at all). I can't really make out… but it may be possible with the balancing valves if they can close enough. And purging involves a full flow of water under pressure; the pressure reducing/maintaining valve may not be able to do that — and going out a drain somewhere. If you don't get wet, you probably aren't purging enough.

If the Schrader valve on the expansion tank is hissing, it may be possible to tighten it up and make it stop. It may not, too, in which case the tank may need replacing. In any case, the tank must be pressurized to the system cold pressure, either with the system drained or with the tank disconnected from the system and empty of water.

nemerrill

OK thanks for the help!

There does seem to be a bleeder on each line. I'm hesitant to touch the balancing valves in case they start leaking.

As for purging, I can use the spigots, but only for a few seconds before the pressure drops and the pressure reducing valve takes literally 5 minutes to bring the pressure back up. I was able to get a good deal of air out purging for a few seconds at a time. I'm thinking I will cut open the supply line and check/replace the reducer.

After the purging I will run each bleeder for an extended time. You recommend closing the balancing valves when bleeding through the bleeders?

Of course, first i better tighten the schraeder valve core on the expansion tank, drain the system, and either reset the precharge pressure or replace then tank. According to the diagram the valve/cover would change color if the tank failed and it has not, so i will tighten/replace the core and check for bubbles with soapy water.

nemerrill

Update. Pressure reducer was clogged. Expansion tank was down to 8psi.

Pulled the valve core out from one of the "balancing valves." Found a guy at a local HVAC shop who called them paddle valves and said they're packed with graphite. New balancing valves are $50 each and primarily for multi-unit buildings. Guy recommended just using ball valves, which may not be ideal but do provide a solution. I also got some graphite in case i want to try repacking

delcrossv

Or, you could go "old school" and use plug valves. Put a little waterproof grease on the plug before installing.

https://www.supplyhouse.com/AY-McDonald-4215-190-10596-1-2-Flat-Head-Gas-Plug-Valve-w-Check-5-PSI