Steam Hammer Season: Noisy Radiators & Pipes

Well it's officially steam hammer season (despite the unseasonably warm weather), and as soon as the cold snaps back in, many of us will look forward to waking up at all hours to the comforting sound of head bangingly loud pipes knocking and kicking themselves around as something, somewhere is screwed up.

But where?

In an effort to get to the bottom of this, Oliver has put together a special mixed audio clip of HIS OWN bedroom noise, and we went looking for answers...

While we found out what the problem is we found NO GOOD total solutions. The explanations below will totally fill you in on WHAT causes the noise and how to fix it if it's your radiator making the noise, but NO ONE seems to have any tips for addressing the problem in an apartment building, when you can't even get at the offending radiators and your super doesn't seem to care.

We open this post up for more help on the matter.

Over at Time Out, they have a list of Top Winter Mysteries Solved, and one of them is the steam hammer, however, their answer is not great:

Condensed water in a radiator gets thrashed around violently when a new head of steam rushes up, causing that hard-to-ignore death rattle. The solution: Place a shim under your radiator to tilt it, allowing the condensation to drain back into the boiler. Or move to a building with central heat.

Over at Parker Holsman in Chicago they got a little more specific and have more solutions:

The banging noises are caused by steam forcing its way through pockets of water. Three problems usually cause these banging noises:

1. People are trying to regulate heat by partially closing or opening the steam valve.
2. Radiator is tilted in the wrong direction.
3. There is a worn-out seat in the steam valve.

To correct these banging problems:

1. For problem one, it is important that radiators always be completely turned off or on. Any partial closing not only causes banging but also results in leakage, damaging your floors and the apartment below.
2. For problem two, a shim is usually placed under the two radiator feet fartherest away from the steam valve, tipping the radiator slightly toward the steam valve (about 5 degrees) to allow the condensed steam to drain back toward the boiler.
3. For problem three, professionl help will be required as the steam valve will have to be replaced.

Obviously, this is not going to help you in your apartment buildind, so we dug further... over at Terry Love's Message Board we found out this useful DIY tip for correcting your own radiator. This is as far as we got:

Just before the steam enters the radiator, it passes a shut off valve, and an expansion relief valve. Turn off the valve to that banging radiator, remove the expansion valve, and soak it overnight in vinegar. Rinse and replace it, and turn on the steam. Does it still bang, but not as bad? If so you have a hard water calcium deposit built up in the radiator, and it captures air in pockets that are irregularly being displaced by hot steam. You could try to clean the radiator with vinegar (or hard water calcium deposit remover [or muriatic acid]) but a wiser bet is to look for a replacement radiator.

Obviously no one has written about how to solve this problem if it's just a pipe running through your bedroom and the culprits are four floors below.

(First published 2006-01-11 - MGR)

Comments (3)

All the problems with steam piping hammer noise are related to near boiler piping. So far i so very few properly done installations. If near boiler piping is done without mistakes, steam system works absolutely quet. Also steam systems must be balansed and properly controlled for proper heat distribution troughout the heating system.

I'm really late to the party here, but i feel everyone's pain. I accidentally over filled the water in the heater. (I live in a building my dad owns so I have to make sure things like this are cared for) It's oil powered steam heat converted from an old coal furnace. The one radiator in my living room doesn't even work and we have no way to figure out why. Anyway I over-filled the water in the steam heater and now it's like somebody is BANGING against the radiators with tire irons. Add to that the creepy steam powered tea kettle whistle and subtract sleep and you have my life for the past few days.

After much stress, I fixed my problem! I will post my solutions here to help those in need, as I was.

I own a 1920's duplex here in Maine with 2 furnaces, one oil, one brand new Weil McLain natural gas, and both units running of single-pipe steam heat. On our new furnace, the water hammer woke up the whole house until I fixed it. Here's I finally did it:

1) I lowered the amount of water in the furnace. When installed, the furnace was 100% full of water, as you can tell by a glass tube on the side. At the top of of this glass tube is a knob that I'm assuming regulates the amount of "safety auto-fill" water that is added to the system to avoid it from firing without water. This was the last thing I did and it seemed to be the one answer. I also:
2) Lowered the PSI from 9 (max) when it was installed to 0.5, (minimum). That is plenty of pressure. With higher pressure and too much water, there is loud hissing from the air valves on each radiator, and several leaks from the radiators.
3) I inclined each radiator toward the return pipe, as you have read in other posts.
4) I replaced all the air valves on the radiators, as they were nearly all clogged, including two in the basement by the furnace which were clogged from years of use.
5) I made sure each radiator "knob" was all the way open or all the way closed.
6) I drained or "flushed" the water from the system by opening a garden-hose-like faucet on the radiator itself, into 4-5 buckets worth. There was a lot of fine black silty sediment from years of no cleaning.

I left the heat at 68 last night and NO water hammers. Previously, the water hammers sounded like someone banging on the radiators with a sledge hammer, repeatedly. There were a few nearly silent noises of expansions of metal (it sounded to me), but nothing that will wake my tenants or me up.

After reading online for days, I thought I was going to have to live with water hammers. Thankfully, my problem is solved! Best of luck to all of you!