How to clean out a boiler with no skimming tapping

acab1975

Boiler pictures here: www.imgur.com/a/iUWms

History: 25 year old Dunkirk PSB-8D, installed by prior Homeowner (Mine since 2014). Water-hammered like crazy first winter I owned it ('14-'15), which disappeared when I replaced the elbow fitting coming into the boiler from the wet return (2nd pic, top elbow fitting)--the fitting had developed a pinhole leak. System has run quietly ever since, until...

Sight glass replaced a month ago. Boiler was full of gunk. Manually ran feed while the bottom valve was removed during the sight-glass change, to push gunk out for a bit.

Now experiencing water hammer INSIDE the boiler at each firing from cold.

I have drained/filled boiler several times (including after the sight glass change), and open the ball valve drain in pic 2 periodically till water runs clear. I've noticed that since the sight glass change, the dirty water is more gray than rust-colored. Also, about 2 weeks ago, opened the drain valve and nothing came out, until I turned the manual feed on and it must've dislodged whatever had blocked water flow.

I'm thinking my boiler is dirty as heck in there, and my wet return/mud leg too, causing the water hammer. Problem is, I cannot find any skimmer tapping anywhere (in pic 4, after removing insulation), or any tappings along the wet return--thanks Mr. Installer!

I would love to give the boiler and return system a good flush...any suggestions for accomplishing this? Should I run a hose in through those tappings for the sight glass or relief valve? Try to open up some of those pipes by the mud leg and hit them with a wet vac?

Thanks, trying to DIY best I can, appreciate your insights.

Fred

@acab1975 , where are the pictures? Typically, the skim port on a Dunkirk is actually a TEE where the riser comes out of the boiler. Not always the case as some installers just used elbows.

EBEBRATT-Ed

you can use the top sight glass tapping if you have too but it's not ideal as it is probably only a 3/4 tapping.

Just be prepared a 25 year old boiler is..........un predictable. I look at it this way. If you don't clean it it will fail. But disturbing it could cause problems as well. Be prepared

acab1975

Fred said:

@acab1975 , where are the pictures? Typically, the skim port on a Dunkirk is actually a TEE where the riser comes out of the boiler. Not always the case as some installers just used elbows.

Pics here: https://imgur.com/a/iUWms

You're correct in that according to the Dunkirk manual, they recommended installing a tee at the riser for a skim port, but the installer here used just an elbow.

Fred

Can't get that plug out upper right, next to the top of the sight glass, first picture? I'm guessing some of your hammer (probably most) is coming from the way the near boiler piping is configured. May be more pronounced with the really cold weather and longer boiler run times/more water dropping out of the steam.

acab1975

Fred said:

Can't get that plug out upper right, next to the top of the sight glass, first picture?

The boiler jacket sticks out far enough over it that getting a good grip on it with a pipe wrench would be difficult, and I was advised by a pro I had over a yr or so ago that it likely hadn't budged in over 20 yrs, and good luck getting it off now.

Regarding your 2nd point, what specifically about the near boiler piping leads you to think it may be causing hammer...is it that janky header just above the vent pipe? Or is that installer only utilized one supply tapping? I've spent some mornings at fire-up waiting and listening for the source & it really sounds as if the hammer is in the boiler itself.

Fred

If you have the owners manual, it will show how it should be piped but, (1) most of those side tapped boilers really should use both tappings into the header. They say one tapping can be used but usually that lends itself to some problems. (2) the risers out of the boiler should rise at least 24" above the boiler. The riser pipe(s) should be the full size of the boiler tapping (no bushings) (3) the one or two riser configuration should then run into a horizontal header, preferably one size larger than the risers, side by side if both risers are used then (4) the two mains should tie into the header, side by side, then (5) the equalizer should come off of the opposite end of the header so that any water that drops out of the steam can fall back down the equalizer end of the header. In your case, the riser is tied into what is both the riser to the header and the equalizer so that when water drops out of the steam, it has no where to go except back down the same pipe that is trying to feed steam to the mains. That can cause hammer. The way that piping is configured, I'm sure it is carrying a lot of water up into the header that then has to fall back into the riser/equalizer.

Fred

Also, that lower tapping on the left of the boiler, below the sight glass is where your boiler drain should have been. That would be the lowest /bottom of the boiler. The drain you are using is probably still leaving an inch or more of water/sludge in the bottom of the boiler.

acl10

I also have a 25 year old boiler. Should I attempt to clean out the sludge or will that make me problems. It doesnt have any low cutouts to drain it so I was going to pump out all the water and replace the water.
Boiler is Enerjet 262,500 BTU input, 214,000 output

acab1975

Fred said:

If you have the owners manual, it will show how it should be piped but, (1) most of those side tapped boilers really should use both tappings into the header. They say one tapping can be used but usually that lends itself to some problems. (2) the risers out of the boiler should rise at least 24" above the boiler. The riser pipe(s) should be the full size of the boiler tapping (no bushings) (3) the one or two riser configuration should then run into a horizontal header, preferably one size larger than the risers, side by side if both risers are used then (4) the two mains should tie into the header, side by side, then (5) the equalizer should come off of the opposite end of the header so that any water that drops out of the steam can fall back down the equalizer end of the header. In your case, the riser is tied into what is both the riser to the header and the equalizer so that when water drops out of the steam, it has no where to go except back down the same pipe that is trying to feed steam to the mains. That can cause hammer. The way that piping is configured, I'm sure it is carrying a lot of water up into the header that then has to fall back into the riser/equalizer.

Thank you. I do have the install/maintenance manual, but it doesn't go into detail on what makes good vs poor piping, as your post here does, especially your point #5 regarding the dual-purpose equalizer and riser on my system--that makes a ton of sense.

I pulled off both sight glass valves (alternatingly) and skimmed for a bit last night thru both tappings then drained and refilled from the drain valve as well. Fired it up and no hammer, but the true test was this morning after the system rested/cooled overnight. No hammer this morning either. Hoping it stays this way for the remainder of the season. Really want to flush out the wet return and mud leg, but with no tappings for those, will probably need to hire a pro to open up the system.

Looking forward to when I can be in charge of the install and piping once this boiler goes--other than the 'paying for it' part.

acab1975

acl10 said:

I also have a 25 year old boiler. Should I attempt to clean out the sludge or will that make me problems. It doesnt have any low cutouts to drain it so I was going to pump out all the water and replace the water.
Boiler is Enerjet 262,500 BTU input, 214,000 output

So you have no way to drain your boiler at all?

acl10

I installed a valve on the baseboard return