Single Pipe - Dry Return Piping

steaminboston

New to site...sorry if I make operational mistakes. Little background....recently installed a Burnham PIN6; dropped header; Hartford Loop with correct A dimension (about 40"); had union coverer cover all piping with 1 1/2" fiberglass; flushed multiple times after install but not skimmed; site glass fluctuation 1/4-1/2" while running; no hammer whatsoever throughout system; using 2 BigMouths on mains and VentRite #1's on 12 radiators.....so 2 questions which I can't find on site:
My 2 dry returns are tied together with their own BigMouths about 12" before the connection and then they drop to the boiler together....doesn't seem to be an issue....no banging....this ok?
Second question....I use about 1/2" of water a week (as measured in the site glass during the peak heating season).....is this normal or average for evaporation?....I estimate it to be about 1 1/2 gallons per month.....looked for leaks/bad vents but found nothing.
Thanks

AMservices

Radiator valves are notorious for leaking. You may need to repack the packing nuts on the radiator valve.
Try to find rusty water marks around the valves.

steaminboston

Ok thanks I'll take a look....so you're thinking that much water per week or month is not normal evaporation?....say getting by the vents before they close?

Jamie Hall

And very small steam leaks can be almost impossible to find. Ask me how I know... Otherwise, sounds good.

steaminboston

Thanks....I'll take a look....good summer project.
Any comments on tying the dry returns together before they drop to boiler?....I've seen comments saying it's ok to do that but then others saying separate drops to wet return....

steaminboston

Also back to the water losage, and I'll check the packing nuts, but does anybody know or has it ever been calculated a % or range or amount that is considered normal for usage?

rbeck

The dry returns are best dropped and tied together below the water line but will work as piped. I believe the water usage is excessive. My sisters boiler with a VXT-24 control which includes a built in water meter is showing 43 Gallons in 8 years of service.

steaminboston

Good info....thanks....so I'm about 3X that usage rate....I'll start looking....and I'm assuming the boilers ok...if it was something from the factory, assuming it would be more dramatic.

Fred

That amount of water loss is most likely just one or two valves or radiator vents that leak a little steam. It may be hard to find but I'd start in any rooms that seem a bit more humid than other rooms. As has been said, also look for any water marks around the valve stem and/or near around where the vent screws into the radiators. That connection can often leak a bit. Do skim the boiler when you get a chance. It may seem to be running fine but sooner or later the oils from a new boiler/piping will affect the boiler performance and don't use any chemicals other than maybe one or two Steamaster tablets.
I also noticed you said you have two Bigmouths on the mains and I think you are saying you have two additional vents on the dry returns. Is that correct? If so, you absolutely don't need the vents at the end of those dry returns. All that does is let steam push all the way down those returns and that offers no value to you. The venting on the mains, after the last radiator run-outs is all you need to vent so that steam can start to work its way to the radiators.

steaminboston

Thanks Fred. Sorry for the confusion...I only have the 2 BigMouths, one on each of the 2 returns....venting seems to be working ok with the returns twinned together.

You're right....I still get probably a cup or so of blackish oily water out of the low point drains.

EBEBRATT-Ed

IMHO two dry returns with steam in them should be tied together below the water line. If tied above the water line cannot the steam main that heats quicker shut the vent on the other return?????

steaminboston

That seems like it could happen.....however they seem to be closing at the same time....1 main/return is about double in length as the other main/return but I took temps along mains at exposed unions and they seem to heat evenly and completely....I also took temps of the BigMouths too with same even result....

Fred

steaminboston said:

That seems like it could happen.....however they seem to be closing at the same time....1 main/return is about double in length as the other main/return but I took temps along mains at exposed unions and they seem to heat evenly and completely....I also took temps of the BigMouths too with same even result....

That's probably not going to tell you anything. One would expect the longer main to take longer to heat to that point, given both mains have the same amount of venting on them. I suspect, as @EBEBRATT-Ed said, steam is passing through the return from the shorter main into the return on the longer main and closing that vent at about the same time. Given it is steam, it will heat both returns so temps won't tell you if the steam is from the short or the long main. Measure the temp on the longer main further back, somewhere before and right after the last radiator run-out. That will tell you if steam has gotten down that longer main, at least past the last run-out before the vent closed.

steaminboston

Ok I'll try that.
Thanks

steaminboston

how about this?....I originally had 2 VentRite 35 Main Vents that I swapped out to the 2 BigMouths because I was trying to vent the mains as fast as I could.

Now, I replace the 1 BigMouth in the shorter main with a VentRite 35 to slow it down (even though it goes against the "as fast as possible" rule)...that way the longer main with the other BigMouth will heat completely....

Fred

It's better if you can just take one of the returns off of the Tee to the common drop and install a separate drop and tie it back in somewhere below the boiler water line. If you don't want to do that right now, buy a Barnes and Jones Vari-Vent and put it on the short main. That way you can adjust it down to where you get steam to the end of the longer main but still vent as quickly as possible on the short main. When you do decide to correct that issue, the B&J Vari-vent can be opened up.

steaminboston

Thanks again. For now, I ended up using a Gorton #1 instead of the VentRite 35 on the short main. (I actually heard the BigMouth close about 10 seconds before the Gorton)
As you can see, I tried different main vents until I read about the BigMouth and had to have them....if I buy anymore or mess around with this anymore, my wife will kick me and the boiler out of the house.
One other thought of why it may be working or could be working ok with the dry returns twinned together....
Pressure always moves from high to low (or the lowest in this case).
In this case at that 3 way intersection, isn't the lowest pressure in the leg going to the Hartford Loop close nipple connection to the equalizer where the steam is collapsing, creating a lower pressure (vacuum?) thus dragging both of those dry returns down or towards the Hartford Loop? (Or at least preventing the 2 dry returns from heading to each other)
Any merit to this theory?

Jamie Hall

I think we've been here before, but I'll stick in my oar again: in my humble opinion, if a steam pipe can be traced back to the header of the boiler, without encountering a trap on the way, it is either a steam main (serving one or more runouts) or a runout (serving one of more radiators) or a riser. It is not a dry return, even if it is a part of a steam main beyond the last radiator. Now that is not to say that it may not be returning condensate to the boiler -- it probably is, if it is sloped that way.

Now if it connected to the boiler, with no traps to interfere with the flow of steam, it doesn't matter where drips are located on it, so long as they are at low points.

So in the present instance, as I understand it, we have two steam mains which go out from the header and wander around for a while and then come back together -- right near the boiler, as it happens, where they have a common drip back to the boiler.

Where should such a system be vented? There is no particular need to vent the section of piping between the runouts most distant from the boiler -- but on the other hand, assuming that the whole thing is insulated, there is no harm to venting the whole thing right at the drip to the boiler either.

Do the ends of these two mains need to be separated from each other and dripped independently? So long as there are vents placed in such a way that steam can get from the boiler to the runouts or risers running in a vented pipe... why?

Now on two pipe systems, the situation is different. There you have true dry returns, which carry only condensate and air exhausted from the radiators. Steam is never supposed to get into them. And... they are commonly joined together at the boiler before the drip, with the system main vents right there. In fact, in many vapour system designs, they have to be done that way!

Perhaps I am being a bit of a fanatic on terminology, but...

EBEBRATT-Ed

@Jamie Hall said" It is not a dry return, even if it is a part of a steam main beyond the last radiator. Now that is not to say that it may not be returning condensate to the boiler -- it probably is, if it is sloped that way."

Jamie, to me that is a perfect description of a dry return.

But, terminology aside. On some jobs two mains tied together above the water line may not be a problem.

However take it to the extreme. One short main and one long main. They come back to the boiler tie together and then drop.

The short main heats fast, sends steam backwards into the long main, closes the long mains vent, condensate in the long main flowing against the steam from the short main.

If they drop below the waterline and then tie together it becomes a non issue

Jamie Hall

Fair enough -- thanks @EBEBRATT-Ed !

steaminboston

Thanks to all. I absolutely agree that 2 separate drops to the wet return is the best way to go but I rather not change what I have especially since it's all been insulated.
So I was wondering at that 3 way intersection, if the lowest pressure would be in the line to the Hartford Loop, created at the close nipple/equalizer connection (where steam is collapsing)....wouldn't both dry returns want to head towards that common wet return instead of 1 dry return going into the other dry return?

Jamie Hall

Nomenclature aside -- if the piping is arranged so that the steam carrying pipes form a complete, closed loop, fed at one point and with runouts on it at various points around the loop, satisfactory venting is going to be very hard to achieve. In an arrangement like that then yes, the loop should be broken into two mains -- and ideally, two mains with pretty much similar lengths (not loads, lengths and diameters) and, if parallel flow, dripped and vented at the ends away from the boiler.

Fred

@steaminboston , I would say not. The point of lowest pressure/least resistance is going to be any open vent, until it closes. Then I would suspect pressure in that area will probably equalize (maybe little less that when it started out of the boiler but remember some of that steam is also condensing in that dry return/main.

steaminboston

Thanks once again to everyone for all the input.
On another note, I did find very small leaks on 2 of my radiator's packing nuts...hopefully, that was it.