Unusual "Water Hammer"

meplumber

Ok.  I have this customer that is getting these random <span style="text-decoration:underline;"><strong>loud</strong></span> bangs from what appears to be the piping.  I have been in the house and heard it twice.  It is a 20 yo W/M 968 with mixed radiation.  Taco zone valves on most.  Caleffi radiant manifold with telestat heads on an above subfloor radiant zone in one wing.  (Big House). 



The banging started about a month ago.  I have ruled out delayed ignition as it did it once while I was servicing the burner.  I have some pinging due to expansion as the different zones heat up but nothing compared to the boom that is heard from time to time.



I have ruled out Domestic water hammer.  I am down to tracing the heating system piping (and there is a lot of it).  But I cannot seem to reproduce it.  Expansion tank is fine although maybe borderline on sizing.  No new changes to the system.



Any ideas fellow basement dwellers?

LarryC

Michieveous Poltergeist?

A month ago ...  The onset of really cold weather?  Perhaps something is physically hitting the heating piping?  A disgruntled resident perhaps?  A collapsing framing member?  A plugged sewer vent line?  Flexing or movement of a tightly constricted cast iron radiator?

 

Any correlation to time of day or outside temperature or wind speed / direction.  Collapsing steam bubble in an overheated line?

 

Is the domestic water on a well?

billtwocase

I'd check

power heads and end switches, and make sure the valves are running the right direction. I have seen them in backwards and when they close, they do bang, especially if another zone is still pushing. Excessive boiler temp, and boiler feed valve, if on, can do it also. I'm sure you have left no stone unturned, but those noises that never occur while you are there, is why we are all gray haired.

billtwocase

also

is there a by-pass on this boiler?

Jason_25

zone valve

 is probably causing issue ive had a few that when multiple zones are open then 1 closes it hammers so manually open all valves then unlock 1 when it slams closed it hammers. A bypass loop is needed to redirect flow to eliminate hammer.

World Plumber

TRV ???

Do they have any TRV? If the water is going the wrong way they can make some noise. I think that Poltergeist maybe visiting my house on occasion. I have a hot water circuit off my steam boiler. Every once in a while I'll hear a bank in the hot water pipes.

    Which brought up a thought. Are the pumps pushing or pulling? Could the pressure in the system have dropped down and a pulling pump be causing the water to boil off inthe pipe? Check that the gauge isn't stuck with the actual water pressure being less.

meplumber

Thanks for the input dudes.

I like the Poltergeist thing.  That may not be far from the truth.



Ok.  House is on town water.  No bypass on boiler.  Triple Aquastat tops out at 185.  I have checked every zone valve that I could physically get to.  There are some in a crawl space that my helper (whose quite a bit smaller) is going to look at this morning.



I hadn't thought of the Plumbing vent Larry.  I will look at that. 



This boom is substantial.  I have heard some pretty loud pipe noises before, this is quite a bit more.  I was certain that it was delayed ignition, but alas, it couldn't have been that simple.  Only one propane appliance.  Checked it. 



I wish I had gray hair Bill, mine left me 10 yrs ago.  If you think of anything let me know.  Thanks.

meplumber

No TRV's.

No Trv's or radiators.  The circs are a mix of pulling and pushing.  I did think of that and purged a little out of each zone.  LWCO and Gauge is working.

Steve_210

Could it be

That a pipe is Jammed in a wood stud or something similar and when it releases it causes the noise. I seen this happen. EXPANSION

Mark Eatherton

Questions...

You said the pumps are pushing and pulling. Not a good scenario. If the pumps are a high head pump, pumping towards the PONPC, and there is a high pressure drop (closing ZV) and the water temps are relatively high (180) the pump could create enough negative pressure to the point that the water will flash to steam, causing a notable BANG. You should be able to see this on the boilers pressure gage due to the pressure shock wave created by the flash.



Is the BANG happening when the water is real hot, or as it is building, or when?



ME

meplumber

Great Point Mark.

I thought about that.  This is a 20 yr old system with no changes in probably 2 years.  Installed and designed by others.  Fairly new customer for me.  I have them slated for a system upgrade in the spring. 



There are a couple of 009's on the return side and a 0010 plus some 007's on the supply side.  I have been trying to catch it doing it.  The 2 times that I have been in the house when it happened, once I was repairing the tub diverter in the master and second I was servicing the burner.  It is such a loud bang, last for only a second, that I haven't had time to look at the tridicator.



When I was servicing the burner, I had justed turned the circs back on, but the burner switch was still off.  Boiler temp was around 160 F.



The fact that it only started a month or so ago is throwing me off.



I have the HO keeping a record for me.  When it happens, What is happening in the house (boiler on, zone calling, etc...)



I have inspected where possible for pipe expansion thru the framing.  Not all of it is accessible.  This is an extreme high end house.  HUGE.  HO and caretaker are being good sports about the whole thing.



Thanks for all the ideas.  Keep them coming.