Added a false water line now hammering

scottnjr

Hi all,
I'm a 25 year hvac tech in NJ. I work on a lot of steam systems, and I've read Dan's books multiple times. I've worn out my Lost Art book until the binding fell apart. Thanks Dan.
On to my problem. My company replaced an old boiler seven years ago on a two-pipe system. It hadn't
heated right until I got involved and discovered that the problem was due to the old water line being much higher than the new and all the old wet returns becoming dry. I installed a false water line exactly as shown in Dan's book, the height of which I got from measuring where the highest return line dips into the end of the steam main. I figured I needed to cover that in water to stop the steam from going back up the returns and stopping flow. Well, it heated AWESOME!!! I was super proud of myself and the homeowner was pretty chuffed as well being that he has been freezing for the last 7 winters while other techs tried all they could to no avail. Today I went back because the system now hammers. It's a Richardson heat vapor system. I also added a vaportrol and ran the pressure at 8 oz. at the time of installing the false water line. The steam mains pitch away from the boiler in two opposite directions with a dry return line along side. on the north side the steam main dips down at about a 30 degree angle and has a swing check in it just before it connects to the (now) wet return which is about three feet off the ground. the return on that side stays high and has a vent then an elbow straight down to the same return pipe. That pipe goes back to the south side of the house to the end of that side's steam main with another swing check and after the check the south side return dips into the pipe. i measured here to arrive at the height for my false water line figuring if I went any higher I would block the vent on the south side return which is only about another 10" higher.
The hammering is on the north side. as far as I can tell, the end of that main is wet now as it should be (right?) During one of my company's attempts to fix the system, they replaced all of the downstairs traps to standard radiator traps. For some reason they left all of the upstairs richardson traps intact. needless to say this didn't help. I dont think that any trap is passing steam into the return because the vent remains open throughout. I took apart the swing check thinking maybe the sound was the valve slapping, but it hammered still. I dont really understand why those checks are there anyway, especially since on this side the pipe is sloped downward at about 30 degrees, wouldnt the swing be open somewhat all the time at that angle?
As you can imagine, piping the false water line is no small task, and experimenting with the height isn't something to take lightly. I dont want to spend all of that time and energy only to find out it still hammers when I'm done. At this point I'm out of ideas. I tried running higher and lower pressure, but it still hammers. I have to figure its due to the height of my false water line, right? So I guess I'm asking what would you guys do, raise it? and by how much? I wasn't there when they removed the old boiler and have no Idea how high it was, but it is now at 42", and that's pretty high, and the old boiler line fluctuated, so I figure I must be at least in range. There are no obvious other causes like improperly pitched pipes that I found to cause the hammering, and it never hammered on the old boiler (of course!!) I don't understand why they ran the return 40" up the wall instead of along the floor either if it was supposed to be wet. Any help or insight will be MUCH appreciated!!
Thanks, Scott

Jamie Hall

First off, I agree -- the swing checks shouldn't be necessary with the water line high enough so that the drips -- the pipes down from the steam mains to the wet return and from the dry return to the wet return -- at separated by the water seal in the wet return (good job on the false water line!). Can you just take the guts out of them?

That said, can you actually locate the hammering? I agree that it can telegraph down a pipe in the most confusing way, but usually one can at least figure out which pipe is causing the problem.

Check very carefully for sags, both in the steam mains and in the dry returns. It's surprising how little sag it takes to ma

scottnjr

I did locate where the hammering is. As I said its on the north side where that steam main drips to the wet return at 30 degrees. I removed the door from that check valve and it made no difference. The steam main enters the return about 10" toward the boiler away from where the dry return dips straight down into the wet return. The check is about 8" back up from the return pipe and when I opened it the water line was right there no higher. Do you think while its steaming that the return is drying and pushing the water around in which case do I move my false up? Thanks for the reply.

JStar

How high is the FWL connection compared to the highest portion of wet return?

scottnjr

Well that's a tough one because the return slopes gradually downward from the south end to the north end where the boiler is. I measured the point where the south dry return connects to the south steam main end. The steam main is higher and then elbows down into a 12" nipple then elbows back level to a swing check then the return comes in right after the check. That return elbows down and has about a 5" nipple worth of vertical then into the return. I measured to the middle of that 5" nipple to figure my FWL height. The pipe gradually slopes down toward the north side then past the north side's main end and return end connections where the hammering is. Those connections are lower than the point where I measured to get my FWL height, so I'm surprised it hammers there and not the south end. The north end dry return is in the rafters and is vented there so no problems with height. The south end has its vent only inches above where I put my water line otherwise I could've just raised the water line up higher but I can't because I would drown the vent and have no heat on that side. The old boiler was a tall coal conversion type, but I can't imagine it's water line was higher than 42", plus it rode up and down with the steam cycle right? And the FWL is static, yet the old boiler never hammered. What am I missing? There are no sags in the pipe or obvious wrong pitches.

Abracadabra

If the system didn't hammer before the FWL was installed, there's no sags in the existing mains. It's related to the FWL. You should be able to use the top of foundation as a reference point to ensure the the FWL covers the wet returns. Got a pic of the FWL you installed? Maybe we can see something there.

scottnjr

aint she a beaut?

Abracadabra

I'm not 100% sure, but that doesn't look right. Is the equalizer line the copper that comes in on a 45? Is your new "A" dimension at least 28"? What pressure is the system achieving? Is it hammering early or late? Can you take a wider view pic? Have you piped that like this:

JStar

The FWL does look very high. The connection should be at least 28" below the lowest steam-carrying main/return.

scottnjr

It's piped exactly like your pic. Better in fact because your pic shows too long a nipple between elbows. It needs to be a close because it will hammer there. The copper is the equalizer. As I said in the post system running at 8 oz. yes there is 28" but at 8 oz I shouldn't even need that much to get the water back in. It hammers late. The water line in the boiler never drops too low. I had to build it high because there is no way other than a water seal to keep steam out of the returns. There was no f&t trap here and as I said the return is half way up the wall. It's a very odd two pipe system. I've never seen one return so high

scottnjr

Also the diagram shows a dry return. Mine comes in wet, and my equalizer comes off the end of the header and down it doesn't go up first.

Abracadabra

Where does the other side of that copper equalizer connect? Did you skim the boiler after the new FWL piping was installed?

scottnjr

As written last post it comes off the end of the header. I didnt skim because we used pre cut fittings. Hence no cutting oil. I guess there could be some flux or pipe dope in there though. I don't see any sign of surging or foaming. The water line is steady Eddie. The hammering is not near the boiler or FWL either

clammy

Does the home heat fine at 10 oz peressure and is the boiler cycling on the vaporstat .You may try putting the vaporstat to say 6 to 8 oz and see if your hammer stopsand if the house continues to heat well , is the hammering occurring at the end of the cycle and when it does occur are all the rads hot or is this happening in mid cycle i have also ran into the likes of yoyrissues ,but being i always run into issue systems i would have possible looked at the return and see what was required to lower it and if it's original with no real way to perfprm a good flush possible replace and lower ,some times even with a fwl if the return is way up at that higher edge of being dry it a fine line you walk .Being your dry return drips into your does the dry reurn have main vents on it and do they have enough venting ?Just asking i think your issue may be in the slopping of your one wet return and the way it is tied in just apossiblablity peace and good luck clammy

scottnjr

I left the vaporstat on 8 oz the day I installed the fwl. It started hammering pretty soon thereafter, but the guy was so happy with the heat he didn't let it get to him. Now it's getting to him lol.
@Jim_R
I appreciate your perspective. Do you have a Richardson system in your house? Yes my company blew it by taking out those old in un-breakable traps. The rads do still all have the original special inlet valves. I haven't tried running at as low as 2 oz. maybe I ought to try that. The dry returns have vents on the ends and they vent fast and the rads all heat all the way across really fast. It starts to bang after it runs for maybe 20 min. We've had some brutal cold so long cycles have been common.
Jim, how are your returns configured? Do you have a f&t trap at the end? Do you have swing checks at the end of steam mains? Does your burner short cycle at 2 oz? How long does it stay off on pressure?

Fred

I'm betting you have a trap somewhere, maybe even hidden, that is failed open.

scottnjr

@fred. I thought that was a possibility too. But that would fill the dry return with steam and close the vent which never happens, wouldn't it? Only air comes out of the 2 vents. There are no other traps only in the rads and all of the first floor were replaced. The second floor are the original Richardson vapor traps. Before I thought of doing an FWL I thought there must've been an f&t at the main ends because I couldn't see how the steam was intended to be kept out of the returns. Then the light bulb went off and I realized it was just water that did the separating. Glad I didn't make the guy buy a couple of f&t traps to add to the pile of money he's wasted on this system already!

Fred

I thought that was a possibility too. But that would fill the dry return with steam and close the vent which never happens, wouldn't it?
Not if there's enough condensate ahead of the vent to cause the steam to condense and keep the steam from reaching the vent.

scottnjr

@Jim_R cool! You still have the original air expeller. This one has two regular vents one on each dry return end. The check by your boiler is the exact ones this guy has. I guess they're there for when the steam condensed and makes a vacuum it doesn't pull condensate backwards? When I took the access off the one I thought was hammering the valve was indeed sucked into its seat by a slight vacuum.
@fred so I guess I need to check the traps with the tempil stick. I didn't have one. I just don't have any other symptom of a stuck open trap like steam entering the returns and stopping the flow. And if the steam is subdued by the condensate in the return then how would it cause my hammering? The sound seems concentrated around that check in the steam main that dives toward the return at 30 degrees. It still hammered around there with the valve removed from the check.

scottnjr

Well this guy has open air vents so no vacuum is possible on the return side. I wonder if that is affecting anything. How does a vacuum develop on the return anyway if there is never steam in there to condense?

vaporvac

Off topic, but I think your boiler's deco design ( @jim _R ) is providing stilff competition for @KC_Jones '. That is outstanding.
Yeah, this is a problem when little understood things are changed in a system. I had multiple companies want to put traps on my rads that didn't need or have them, just ells with metered valves. They didn't get how that worked.
Just glad I figured the "dead men" knew what they were doing and showed them the door.
I guess there's no chance your company kept those old valves.

scottnjr

hope this helps

JStar

Is the FWL line above the height of that main?

EBEBRATT-Ed

If you touch the two pipes that drop down where it is hammering are they hot? Steam hot , can you tell where the waterline really is with an infrared. Somehow it seems like those connections are still exposed to the steam somehow

clammy

If that green line is your false water line level you may not have enough height to keep them covered but that also depends on how much left over pressure you have in the end of those ot that main that banging .In the past when i could not do a fwl i built inverted u seals for end of mains which tie together at the end of there run i piped straight down belew my wet return and came back up in the bottom .Of course a tee w a mud leg is installed and provision to fill w water to prevent banging same as a fwl.When you can t get your dimension and can t re do the return but need a good seal between your dry return and end of your steam main this is a handy trick .I used this in a very large apartment building which was a single pipe and had alot of issues some guys put f and t and condensate pumps nothing worked ,i dripped the mains into seals and that was that.I have seen varations of this type of water seals at end of mains in a few older 2 pipe systems that where lucky enough not to get knuckleheaded and had just about every thing original .The water seal trick is in some old steam fitters hand book possible a hoffmann steam fitters or a audels hope this helps peace and good luck clammy

scottnjr

@clammy yes i have seen that water seal in "standard"two pipe systems a lot. This is a vapor system remember. Not that the trick wouldnt also work here. I just think they achieved the same thing here with the wet return. It proved correct when the system heated so well, I just have to get rid of that pesky banging the neighbors can hear down the block. You would think that the hammer would be on that left side where the water line is so close to being too low. The right side is lower and wetter, so why does it hammer there? Also, anyone know what the swing checks accomplish here?

EBEBRATT-Ed

Good Idea CLAMMY that could be the fix

scottnjr

its a good idea, but why wasnt it necessary with the old boiler?

JStar

Something seems very wrong, especially for a Richardson system. All ends of mains should drop into dedicated wet returns.

Abracadabra

How close is your FWL level to the wet return in the hammering area?
I assume you've got good venting at the point where the main drips into the return?

scottnjr

@jstar they do. now that i built a false water line.
@Abracadabra im not sure what you mean about the level. there is no vent on the steam main only on the return. and its a standard steam vent, and a richardson had an expeller that closed on vacuum. i dont know if we lose something with only an älways open" vent instead.

Abracadabra

As @JStar asked, all your mains drop into wet returns. You said "yes". At the point the mains drop into wet returns, you have appropriate main venting? If your FWL is at the level of your returns, your returns might be partially full of water. You want to make sure that they either stay dry or completely wet, not something in-between.

scottnjr

@Abracadabra Its two pipe, so the air is pushed through the rads, through the traps, then out the return line to the vent on its end. Why do we need a vent at the end of the steam main? I hear you for sure on the fwl level and the pipe being partially full only. I didn't really see a choice here because of that vent on the left on the second floor that another plumber put in for his own reasons. It's not very much higher than the water line I pictured here. So my hands were tied as far as going any higher to bury that line in water because I would cover that vent on the left side second floor which is the only vent for that whole side of the house which would lead to no heat. The vent on the right is nice and high from the water line. But since that vent on the left side second floor was there on the old boiler and it didn't hammer, I thought it shouldn't on this level because I really had only a few inches to play with in that vertical nipple of the return, I thoght it must've been there. Where else could it have been you know? But that second floor vent was definitely concocted by someone with a limited understanding of how this system works, so it's a variable that has to be considered. But I think he may have piped it out of where the existing air eliminator was in the return so it would've been that high anyway. I'm out of ideas that don't involve major calories burned

scottnjr

But the return is below the false water line by 6" at least by that point and you figure the returning condensate stacking up depending on boiler pressure, which I'm running at 8 oz. I tried at 1 lb. and it still hammers. Haven't tried it at 2 oz like @jim_r runs his at. I don't have much faith though. Something is still not right in the piping, I just have to make the right choice in the remedy.

EBEBRATT-Ed

As Abracadabra said "You want to make sure that they either stay dry or completely wet, not something in-between". I think if your getting hammering that somehow you have got "something in-between.

scottnjr

Well put sir. Now what do I do?

scottnjr

The more I look at that diagram I think why the hell didn't they just put that return on the ground, why put it so high by the waterline? That's all original piping also.

EBEBRATT-Ed

By the way Abracadabras FWL drawing is the best one I have seen

clammy

I realized yours is a vapor system and that trick works on1 and 2 pipe espicially when have left over pressure in the main just make your seal deep enough for your remain pressure does not blow through .I ve had 15000 sq ft homes heat with 4 to 2 oz The more pressure left over in the end of your mains the more stacking you will have and more hammer .Always have to weight out where a system merits afwl or just simple lower your existing to get that water seal ,Peace and good luck clammy

BobC

The original boiler may have had a higher water line.

Bob

scottnjr

I went back yesterday because I thought I had the solution. Someone installed a main vent in the main that's hammering now. I don't know what they thought that would accomplish, but I didn't think it was detrimental. I didn't even include it in the drawing I made for here. I became convinced that it was opening after all the traps closed and causing a quick pressure change and then hammering. I went and removed it and ran the system 30 minutes with no sound. I thought I had it and then...bang bang!! I had my ear to the return side vent and I could hear a lot of condensate moving around. I also set the vaportrol to 2 oz. the rads heated quickly and all the way across. So I left it there. I left with still no solution. The only good thing is it took a half hour of continuous running to hammer, and most cycles won't be anywhere near that long.