Okay, new house to my wife and I... we've had it less than a month and two days ago it was time to turn the heat on. This is an old hot water system, no pump (works by gravity) in a three story house.

The radiator in the master bathroom wasn't full, so I tried to bleed it. Just a little air came out, and it didn't fill. The bottom half of the radiator was warm so the radiator shutoff isn't stuck closed. Off to the basement I went. The auto-refill on the system comes from the main water line, is "stepped down" to 12psi through a reducer and then has a 30psi relief valve going directly to a drain. I have two boilers run in parallel (one coal - unused, one gas), and each has an "Altitude" gauge on it with no units listed (is it psi or 'feet' of water?). They both have red needles set at "25", and had black needles (the actual measuring ones, and neither are stuck) reading at "25" on the gas and "20" on the coal. These things are 75 years old or so, so I don't expect them to be 100% accurate.

Anyhow, I pulled a little handle on the 12 psi "step down", hoping that it would help me auto-refill (I have no idea if the handle is lets the water pressure get to 12 psi or if it bypasses the 12psi and lets the full "line" water pressure through). My wife sat upstairs bleeding the radiator. Pressure gauges on the boilers go up, 2nd floor radiator is bled. Yay.

On to the 3rd floor. All of these radiators are almost empty. They all have brand new valves on them, so I guess they were drained for the valve installation. Unfortunately, the guy who owned the place before us passed away, so I couldn't even ask him. So, same thing as before, I pull the handle on the pressure step down, wife bleeds the radiators. Well, this time I stop early and say "uncle". The altitude gauges on the boilers read "32" and "27", and I decide to call it a night before I screw something up.

I know that it should only take about 15psi to fill up the water system (guess that the top of the topmost radiator is 35' (max) above the pressure gauges... 35'/(28"/psi)-> 15psi). Sooo... what's going on? Are my "altitude" gauges on my boilers measuring "vertical feet of water" or psi? Am in endangering my system/boilers by pulling that handle on the pressure step down in an attempt to fill my radiators?

Thanks in advance!!!

labman

Ordinary pipe and most pressure vessels are built to stand 150 psi. It is possible the radiators may not have been designed for that pressure or no longer will. Likely the water is 90 psi. or less. Maybe the best thing to do is to start with a new pressure gage. You should be able to pick up one at a hardware or home center in the plumbing supplies. Most gages work fine with water or air. Once you are sure you have the 15 psi. or more, try to fill the radiators. If it doesn't work, post back.

knightpitt

good call. I'm going to try to find one of those water pressure guages that you can screw into a faucet-hose-type thing on my way home today. The whole heating system actually has two drains, so I figure that if I can actually find the real pressure (in psi) of the system, I'll have a much better idea what's going on.

I was just hoping for a reply that said, "Yeah, those 'Altitude' gauges are really just converting the water pressure in psi to 'height of water'. It's very common in those old boilers... blah blah..." Oh well. I guess I'll have to find out for myself!!!

labman

Why not post the question on the gage in plumbing? Unlike some areas here, Tom know his plumbing and goes back to systems like yours. A lot of people here, like me, know enough to solve some problems, but few match Tom in his area.

caibuadday

are you sure this system is WATER not steam.... it is very hard (impossible) for a hotwater system to work without a pump ....FYI 35' = 15 psi ...(35x 0.433)...................hot water system have 2 pipes (in/out)....steam ONE pipe only.............steam boiler only require 1/4 to 3/4 water fill of the boiler..... water may (99% of the time) come out of radiator if radiator is full of water

labman

Caibuadday brings up a very good point. If your radiators have a big pipe going in one side, and a little doodad coming out and stopping on the other side, it is a steam system. You only want the water up to the top of the sight glass on the boiler itself.

Older hot water systems did work without pumps, but would have a large pipe to each side.

Sorry about suggesting Tom. I forgot about him living in Florida and lacking experience with heating systems.

knightpitt

Yep, I'm positive that it's a hot water system. There's a big pipe in and out of each radiator. This thing is an absolute dinosaur. No pump, though. It works, just not efficiently.

For an update, I purchased a water pressure test gauge yesterday from my local plumber's supply store. My wife admonished me, "You got one of those cheap air-filled ones! They always break." me: "sorry, dear." My wife works as an environmental consultant and occasionally works in the field in groundwater remediation systems, so she knows her gauges.

Anyhow, I put the gauge on one of the boiler drains and opened the valve. I was reading about 13-14psi on the new gauge while the "Altitude" gauges were reading around 30-35, and this was while the boiler was warm. Good! This put the whole situation into a much better perspective. Those "Altitude" gauges are most likely reading pressure in psi * 2.33 = feet of water column. So, technically speaking, the water column reading could be 70 (=30psi) before the pressure relief would go off. So, that's very good news.

I didn't bother bleeding the 3rd floor radiators last night, but I'll probably try to do it this weekend sometime. We'll see how it all goes!

No problem! It never hurts to try. He might have lived another life in New Hampshire fixing people's old boilers.