Water Hammer...First time in 15 years??? Really?

AdmiralYoda

Got a weird one. My house was built in the 1880's, Peerless boiler is 40 years old and has performed flawlessly. Near boiler piping is a little iffy but the risers are about 3-4' above the water line so I think that has made it work.

I've had the boiler off for a few days since its been warm but I turned it on today to break the chill. Thermostat said the house was 66 and I turned the heat to 68 degrees.

After a few minutes I start hearing BANG, BANG.... Definitely water hammer in the mains. In the 15 years I have been here with this boiler and piping, not once have I had water hammer. System has always performed flawlessly.

So I go into the basement to check on things and notice the site glass is almost empty, about a 1/4" away from the bottom of the glass. I just checked it two days ago so I knew something was up, so I cut the power to the boiler. After about 15 seconds the site glass returned to about half way full.

I turned the boiler back on and watched it cycle. The water still dropped a couple inches and didn't bounce more than an inch....but it still was much lower than usual.

No new work to the steam system so there shouldn't be any oils that were introduced. No construction so no accidental "re-pitching" of pipes. I've been using Rectorseal 8-way for years to keep the pH around 10 or so. 8oz only for the entire boiler. Zero corrosion and the water stays very clear.

It looks like I'm getting surging and/or very wet steam....for the first time ever. No foaming or weirdness in the site glass.

Thoughts?

AdmiralYoda

I should also mention that the water hammer happened even before the main vent was even warm. Its a Barnes and Jones Bigmouth and it did close once the steam got there. Maintenance was performed by New England Steamworks last November-ish. They said everything looks great.

neilc

have you serviced your pigtail ?

post pictures,

pressure gage separate, or with the Ptrol, after the pigtail ?

AdmiralYoda

It is a single pipe counter-flow system. Pigtail is 2 years old, serviced and cleaned in November of 2021. The pressuretrol is set as low as it will go and is a backup. The vaporstat kicks in at about 12oz of pressure with an 8oz differential.

Best I can do with pictures for now. There is no equalizer between the two main risers. The main on the right services one side of the house and has a Bigmouth at the end. The main on the left loops back to the other side of the house but does NOT have a main vent.

neilc

is that top half of the sightglass wet (and flowing) ?

maybe too much purple, and the water is boiling violent inside?

is that skim piping on the left? with the safety valve?

AdmiralYoda

@neilc Top of the site glass is wet yes. I don't think it has too much Rectorseal, its only 8oz and the pH is about 10. Yes I have a skim port and valve next to the safety valve. It was skimmed in November with the normal service, but I plan to do it again.

It just amazed me. I'm in my living room and I heard the mains banging and instantly knew what it was....and it was the first time I've ever heard it in this house.

Jamie Hall

could something have shifted slightly? Wouldn't take much.

AdmiralYoda

@Jamie Hall I don't see how. Was working two days ago, absolutely nothing has happened in the house that could disturb a radiator or piping for years. No construction, projects, remodeling etc. Just living in the house the same as we have for the past 15 years.

I'm going to skim it tonight and try and flush any junk on the bottom, refill with plain water and let it run for a while to drive out any free oxygen. I'll chill out by the boiler and observe.

AdmiralYoda

Status update. I drained a bit of water from the LWCO and boiler drain and it wasn't too bad. Some rust but no sludge.

Skimmed the boiler for couple hours until the water ran cool. Nothing out of the ordinary but the water was pretty rusty. Probably couldn't see through more than a couple inches of it. Flushed it out good, filled it up and added 8oz of Rectorseal.

Fired the boiler up and watched. Worked perfect. No water loss, no excessive bouncing on the site glass. Just normal. Maybe the Rectorseal cleaned enough stuff that the water was nastier than I thought and it caused some surging. Seems normal now? We'll see.

ChrisJ

How long ago were any new vents installed, including that big mouth(s)?

AdmiralYoda

Big mouth was 3 years ago. Radiator vents are Maid O' Mist's that are 2 years old. System is pretty well balanced. The MoM's seem alright and the Big Mouth closes once steam hits it. No evidence of leaking.

ChrisJ

Any chance it always does this during a very cold start and you just never noticed or weren't home?

Aside from that no idea. I'd just be happy its gone and not put too much thought into it.

AdmiralYoda

May be possible that a very cold start did it. It would definitely be a recent phenomenon, experimented with a 2 degree set back a few months ago and this never happened on fire up.

After refilling the boiler it was stone cold when I just fired it up. No problems at all. The site glass is very clean now, makes me thing the water was nastier than I thought.

mattmia2

obviously if it starts priming or surging for some reason there is no place for the water to go ut i to the system.

A hanger could decide today was the day to fail or a pipe that is wedged somewhere could let loosed causing it to sag, no need to alter anything, either of those things could let go after decades of being that way.

reggi

Was the brand new 3/4" x 24" Iron Wrecking Bar laying on top of the boiler when you initially turned up your thermostat and the banging started ? You sure that wasn't banging around? 👀

SteamingatMohawk

Here's a SWAG. Since the pipes expand and contract when heating up and cooling down at a different rate from the structure of the building (my system ticks and creaks occasionally), could there be one or more locations where the piping could change slope ever so slightly depending on the temperature conditions in the building. Perhaps, once the system heats up and warms the structure, any sitting water could then flow back to the boiler.

Not being a chemist, what is the internal surface condition of the piping, when chemicals are used? Smoother or rougher than untreated? Tendency to hold water back or build up corrosion products in "low" points?

AdmiralYoda

@reggi Nope, the crow bar is long gone. This photo was from about a month ago but nothing has changed.

@SteamingatMohawk Possibly. I intend to re-pipe the boiler soon to a standard drop header and equalizer. I also want to bust an elbow on the other main and install a T so I can put a vent on there. I'll find out the condition of the old pipes then.

My system doesn't make a whole lot of rust. The water stays pretty clear but this is also the longest I've had Rectorseal in there from a boiler fill in November. Perhaps there was enough junk and rust to knock loose that after 6 months the solids and Rectorseal started to become a problem.

For now, the problem seems to be solved. Since the heat was on yesterday the system hasn't kicked back on and everything is stone cold. I'll let it cool down a bit more and then fire it up and see if the problem duplicates itself. If not.....its fixed.

BobC

I also think some of the piping has been on the line when it comes to slope and some building settling may have pushed things over the edge. I your flushing does not prove to be the long term fix I'd start putting a level on all horizontal piping to make sure all it's slope is still there.

Bob

ChrisJ

Why would piping sloped wrong or sagged suddenly make the boiler blow water up into the main(s) and cause condensation in the upper half of the gauge glass?

mattmia2

ChrisJ said:

Why would piping sloped wrong or sagged suddenly make the boiler blow water up into the main(s)

It could collect condensate that was previously draining back to the boiler to collide with steam from the boiler.

reggi

For instance.. Your boiler , piping  , radiators etc. are completely empty, void of any water/moisture, bone dry to begin with. . 
It takes 8 gallons of water to fill your boiler to the proper height in the sight glass..
You run a cycle or 2 and shut the boiler off

and completely drain the boiler ( for sake of argument you empty the boiler completely)
Now you measure the water drained out and How many gallons do you have ? 8 ? No now you have condensate at the bottom of the radiators , water in your wet return, water in low spots in your pipes etc.. so let's say you get 6 gallons back?  That will leave 2 gallons of water throughout your system in various nooks and crannies..
Now some of this water isn't at rest.   it's elevated and seeking the lowest level..Gravity.. So it's maybe condensing, dripping, rolling etc. until it can't overcome. Gravity ..it could be dip , low spots, pipe connections but somewhere along it's trip... from different sources.. the water stops moving and if it's still being fed it's getting deeper and taking up more space in the pipe...
Now having the boiler off a few days perhaps you gave the system a "Rest" where these "Water seeking lowest point" didn't have to overcome a running boiler and were allowed to drain to points lower than possible otherwise.... giving larger pockets of water , water where water doesn't usually get to ( 2 Days off is a big break after a cold season).
Now your boiler water level is at the right level and you start it up then shortly what happens? What's been dripping back into your boiler the past few days? 
Water Hammer.. makes sense ?
Right.. I serviced a radiator valve earlier this year from a second floor radiator and I wiped it and it was purple so that stuff will travel and who knows how long it will be working on your entire system even after) if you go to plain water.....So the constant cleaning will be removing more build up and returning it through your pipes to your boiler, the more vigilant you must be