No purge water flow when bleeding boiler

JLTSKFL

Hello.

My parents have a very old Hydro-Therm boiler. I attempted to bleed it as there's audible air in the lines. When doing so, I cannot get any flow out of the hose. At best there's a trickle, and I'm not sure I'm not just draining my zone runs.

This setup has the circulation pump on the return of the boiler, and two zone valves on the heat delivery side. There are two returns from each zone, each with a bleed valve and smaller finger gate valve (or balance valve). The water make up goes to a brass tee, with the bladder tank on one side, and the outlet going to the inlet of the circulation pump.

Nothing I do causes water to flow out of the bleed hose other than a trickle at best with the water supply on and the bleed valves open. Originally, the gate valves were closed, so I opened them, which should produce a direct path to the bleed hose. Nothing. I then opened the zone valves as well. Nothing.

With the zone valves open by manual control, there's no flow. With the system powered on and the zone valves open, there's a sound of rushing fluid, but that might just be the circulation pump causing that.

Somehow put back together the system is maintaining 10psi. The bladder tank is half full by tapping it.

What am I missing?
- What in the system is maintaining 10-12psi? Something hidden? Regulators are not small.
- Why is there no flow from the city water connection? Possibly stuck or clogged check valve?
- I'm assuming unless there's no strong flow of purge water there's no way to force air bubbles from the 2nd floor down and out.
- Do I need to install a pressure reducing regulator?

Thanks.

neilc

can you post pictures ?
of the pressure gage,
and of the makeup water feed,
and a general wide view of the boiler, piping, circ, tank,
all in one or 2 shots, different angles, floor to ceiling

neilc

it does not sound like you have good pressure there,
pictures and we can determine where and how,

JLTSKFL

Here is a diagram of what I think the system has. And also photos of all devices. I should add, I'm an engineer who owns an industrial maintenance company for 30 years now, so you can get as technical as you want.

Jamie Hall

Well, question one here -- can you boost the system pressure by opening the manual feed valve? If not, either there is something wrong with that valve or the pipe to it, or your house water pressure is that low (unlikely), or the gauge is busted.

Whether the little balancing valves are open or not, if you have pressure and flow at the manual feed and you open a bleed valve, you should get a good flow of water with the corresponding zone valve open.

JLTSKFL

If by manual feed valve you mean the hand valve from the city water supply, it is always in the open position. It has been in the open position forever, even in operation. That's why I was wondering if there was some hidden component restricting water pressure, because unless my physics are wrong, when city water is connected the whole system should be 30-40 psi. House pressure is very strong.

So without a pressure reducing valve, the city water supply should normally be off all the time and turned on when needed?

My best guess is the check valve in the 3-way bladder tank connector is stuck.

Jamie Hall said:

Well, question one here -- can you boost the system pressure by opening the manual feed valve? If not, either there is something wrong with that valve or the pipe to it, or your house water pressure is that low (unlikely), or the gauge is busted.

Whether the little balancing valves are open or not, if you have pressure and flow at the manual feed and you open a bleed valve, you should get a good flow of water with the corresponding zone valve open.

neilc

can we get a better wide angle view?
show it all in one shot,

last picture, the line connecting at the tank, should be your makeup feed, any valves or fittings elsewhere on that line, show them and the far end,

the pressure gage is only at 8, too little for 2 floors,
you're aiming for 12~15,
gotta find your feed valve(s),
actually, that's your feed fitting at the tank, try rapping on it, it's stuck,
is the other end of that feed line open ?

not sure you'll get a good purge from that fill valve,
you might need to add a washing machine hose between house pressure, and a boiler drain,
typically you'll try to get system pressure up to 20~25 to get a good purge going,

JLTSKFL

It's hard to show an overview because the system is ancient and everything is positioned behind the boiler. I attached a photo anyway.

The system reaches 15psi when heated.

I've pictured the feed valve below. It's a simple water gate valve, and it's open. The other pipe that goes to the whole house filter is the house drinking water supply. The pressure in this house is very strong.

So the basic answer here is, with no pressure reducing valve, there is no other component that would reduce flow from the makeup water feed, and the check valve in the bladder tee is likely stuck closed? AND, with this setup, the feed water valve should be closed during operation or the system pressure will rise to city water pressure? This valve has always been left open, even after two HVAC 'experts' serviced it over the last two years. Oy, vey.

Also, some of the finger-small gate valves close, some just spin around 360. I'm assuming they should and can be replaced with standard gate valves? Is there anything special about these one-piece bleed/gate valve assemblies?

JLTSKFL

JLTSKFL

This is interesting. Flush from one drain valve to the other..... Good idea.
I need to fix all of this first. Can I add a simple 12psi reducing regulator to the system after I replace the check valve?
Thanks everyone!

neilc said:

you might need to add a washing machine hose between house pressure, and a boiler drain,
typically you'll try to get system pressure up to 20~25 to get a good purge going,

neilc

that fitting at the tank is a pressure reducing / tank check valve,
the gate valve at the other end of the feed line could be left open, needs to be when purging, but the reducing fitting is not adjustable, or fit with a fast fill, so best it would do is 12 psi,
to purge you want to bump the system up closer to 20 to push your air down as you mentioned,

https://www.supplyhouse.com/Amtrol-109-15-Fill-Control-Valve

you know you need to purge one loop/purge bib at a time, certain valves open and closed to do each, right?

JLTSKFL

Hello. Def understand to purge one at a time. The pressure and flow would drop to nothing if trying to do more than one.
So I got as far as looking at the Fil-Trol fittings, but could not find any specification documents that said it was also a 12psi pressure reducer. So I'm glad I heard from you, and now it makes more sense that the make up water was left on. I'm ordering another complete 110 unit with valve body, and new drain and balancing valves. I'll also install a flush bypass. One question though, some have said don't replace balancing valves with ball valves, and others have said the one-unit drain and balancing valves ARE ball valves inside. I'm assuming you've seen the inside of balancing vales, are ball valves fine to use instead?
Thanks for all your help!!

neilc said:

that fitting at the tank is a pressure reducing / tank check valve,
the gate valve at the other end of the feed line could be left open, needs to be when purging, but the reducing fitting is not adjustable, or fit with a fast fill, so best it would do is 12 psi,
to purge you want to bump the system up closer to 20 to push your air down as you mentioned,

https://www.supplyhouse.com/Amtrol-109-15-Fill-Control-Valve

you know you need to purge one loop/purge bib at a time, certain valves open and closed to do each, right?

neilc

there's a spec in the link , and 2 videos I did not watch,

balancing with ball valves can be finicky, there are better valves if you want easy precision,
but ball valves will do you there,

leonz

Where is the air scoop? if there is no air scoop with an automatic air bleeder OR a steel compression tank with an Internal Air Separator and airtrol valve you have no point of pressure change.

Have you tried raising the boiler water temperature by pushing the thermostat all the way up or raising the high limit on the aquastat to 180 degrees Fahrenheit and then purging the air in the system?