leaking vents

eagle0031

Have two pipe steam the returns tie into wet return in the basement. On each 3/4 return just below the ceiling there are steam vents. The plumber changed all of these to vari vents (ugggg!!!!!) because the two closest to the boiler were dumping water when the system starts up. There is a check valve on the return before it enters the boiler> I found between the boiler and the check valve it was clogged. Thinking the condensate was stacking up in the return and these being the closest to the boiler is why the were dumping water. I haven't heard back from customer was looking for feed back. Never seen the vents mounted like this in the basement on each return

Dan_NJ

Isn't this why the hartford loop was invented? The vintage 1980s Weil Mclain training video talks about check valves around the 17:00 mark:
https://www.youtube.com/watch?v=21pMUZlTx8s

Jamie Hall

Dry returns on a two pipe system must be vented -- generously! -- as that is where the air from the radiators escapes.

However, they should never see water. Your theory that water was stacking up behind the wet return due to the combination of the check valve and just being sludged makes sense -- or would, if it happened later in a cycle. The other possibility to watch out for, though, is if the boiler pressure is too high water will back out of the boiler, Hartford loop or no (there is one, isn't there?) and through the check valve which probably couldn't seat against such a low pressure and flow, and up towards the dry return.

Keep in mind that until the system really gets cranking (and maybe not even then) that dry return is at atmospheric pressure, so you need that 28 inches per pound pressure above the boiler water line.

nicholas bonham-carter

I’m not sure a check valve would be needed, except to compensate for over pressure. That arrangement creates a bottleneck, which can collect a lot of debris.
More venting is needed, but I think you have heard the last from the customer-until their problem becomes more severe.—NBC

eagle0031

Jamie Hall yes there is a Hartford loop and yes I understand the vents purpose just not common in my area usually mounted at the rad. Good point about the stacking and how early it’s happening. I agree no need for the check valve. This is a new account for us and new owners so I’m assuming this has been an on going issue. I lowered the pressuretrol to .5 and 1 on the cutout. There are 76 Hoffman main vents on the ends of the supply line. Wondering if someone possibly removed a vapor stat and installed a P404a in its place?

eagle0031

Well customer called back starting pushing out water again out of the two vents on the dry returns closest to the boiler. Pressuretrol is as low as possible!!! What’s puzzling me if this has been on going problem before these people moved in or not? This happens on the start after running 10 mins or so?

JUGHNE

Did you remove the check valve in the return?
Sometimes for a quick fix you can open the check valve and remove the flapper/gate which might not be opening.
You said there if a HL on the return also?

Are these the only air vents in the entire system? None on the rads?

eagle0031

No I did not remove the check. I did open the check and the check itself is free. I put a hose on the return to add water and saw the check open. Yes each dry return from each rad has a vent on it in the basement. There are no vents on the rads.

nicholas bonham-carter

The check valve is probably a bandaid for keeping the water from being pushed out into the returns by over pressure.
With a gravity return, the check valve can interfere with the water returning.
Put a clear plastic hose on the boiler drain, and see how high the water is being pushed up by pressure. If it’s up to the main vents, it’s a problem, as they will not be able to breathe.—NBC

eagle0031

NBC... I’m ahead of you partially I removed the main vent and installed nipple elbow and nipple to see if I got water out of main vents I did not... I was going to try doubling my main vents to see if helps. There is one #75 Hoffman I was going to double them. I agree with you that the check was an attempt to correct this issue. It does not appear new or recently installed. I will try the clear to on the return to see how high it pushes. Appreciate your thoughts

nicholas bonham-carter

With today’s knowledge of main venting requirements, a Hoffman 75 is good for only about10 feet of 2 inch main.
Try leaving the main vents off for a short test to see if the water in the returns is rising up as high as the vents, (and overflowing), as the boiler first begins to make steam.
I suspect your pressure may be going above 1.5 psi, and the clear hose test could confirm or deny that.—NBC