What's with the water in the bottom of my radiator? Yet Another Clanging/Hammering Scenario.

HarborAce

Hi,







I've enjoyed and learned a lot from posts in this forum.  Thank you all for that.







I have a specific issue for which I can't seem to find a solution.  I'm

hoping the knowledgeable folks here can help me out.  I was a plumber

for three years shortly after graduating from college, but now work in

an office.  I've worked with a fair number of heating systems, so I know

a little about steam heat (but not enough).  Here is some background

information about the system.







I live in half of a rented house where the first two floors are heated

with steam radiators.  The top (third floor) has electric baseboard. 

The boiler for the one-pipe steam system is in the partially finished

basement (below the first floor).  My bedroom is on the second floor on

the opposite side of the the duplex as the boiler, which sits on the

outside wall.  I'd say the run across the basement is about 10 feet to

an elbow, then another 25 before the pipe that leads up the two floors

to my room.  Many of the feed pipes are two inches (i think), but the

feed pipe that leads to my bedroom's smaller radiator is an inch (or

close to it).  Here's a picture of a similar radiator:







<a href="http://upload.wikimedia.org/wikipedia/commons/f/f1/2006_400x700_one_pipe_steam_radiator.jpg">http://upload.wikimedia.org/wikipedia/commons/f/f1/2006_400x700_one_pipe_steam_radiator.jpg</a>







When the system kicks on, especially after sitting cold for a few hours,

the men with their hammers come out and bang the heck out of some of

the pipes.  Much of the system is fairly quiet, but the pipes leading to

my radiator make the most noise.  The sound starts in the basement and

works its way up to my bedroom.  It subsides once the system is up to

temperature.







If I'm sleeping, which I really enjoy doing, the sounds coming from my

radiator will wake me up pretty quickly.  I tried a few of the basic

fixes.  I raised my radiator's vent end so the condensation retreats to

the boiler properly.  I checked the pitch of the pipes in the basement

and pitched them back to the boiler as best as I could without doing

anything drastic.  I made sure the supply valve was fully open.







Despite these minor adjustments, the system clangs as loudly as it did

before.  Finally having a free afternoon and being fed up with the

situation, I decided to go beyond the expectations as a tenant and

disconnect the radiator to look for blockages and places where water

might collect.







Upon disconnecting the radiator, I noticed that the valve was in decent

shape.  I looked inside the bottom chamber of the radiator and didn't

see any blockages.  I used my snake to make sure I wasn't missing

something.  What I did notice is that the radiator's vertical chambers

extend below the line of the feed pipe.  This means that water naturally

traps at the base of the radiator.  I was pretty surprised at this

discovery.







I tilted the radiator to about 45 degrees and drained the water, which

was perfectly clear.  When inspecting the boiler earlier in the week, I

noticed the glass was quite dirty, so I was surprised to see clean water

in the radiator.







My first question is:







Are those chambers that sit below the pipe normally that low?  And if so, how come all radiators don't clang that loudly?







My next step is to insulate as much as the piping as I can leading to

the radiator.  I think that and maybe another check on the pitch of the

pipes might quiet those noises.  I'm pretty sure the cause of the

clanging in the radiator itself is the water build-up in the bottom of

the aforementioned chambers. 







Does anyone have any other suggestions or things to look for that might

cause the incredibly loud hammering, particularly in my radiator?







The pressure control is set to about 2 lbs, which I think is okay.  I don't feel comfortable working with someone else's

boiler, so I don't think I should adjust anything there.  Since most of

the system is quiet, I assume my problems are in the piping, valve,

radiator, or vent related to my unit..  I believe the vent is

functioning properly, but I'm considering buying another one.







Any and all advice is welcome.  Thank you for taking the time to read this likely too verbose post.







Best,







Erik

Jamie Hall

Feed pipe

may be too small.  And it does need adequate pitch, but you've checked that you say.  I don't have my tables handy here -- do you have a copy of Dan's The Lost Art of Steam Heating?  It has all the necessary sizing tables.



Pockets at the bottom of the radiator are common enough, and I'm not surprised that the water was clean -- it is, after all, distilled water in a sense (though I wouldn't go drinking it!)

HarborAce

Trapped Water

Hi Jamie,



Thanks for the response.  I think the noise I'm most concerned with is that which comes from inside the radiator.  I believe it is pitched sufficiently.  The feed pipe comes straight up from the basement, so there isn't a place where water can get trapped between the basement and the radiator.  I think the trapped water I mentioned at the base of the radiator is what causes the hammer.



So that trapped water at the bottom is normal?  Without tipping the radiator 45 degrees, it's impossible to drain the water out, which means it naturally sits there.  I guess I don't understand why all radiators don't hammer if they naturally collect water at the bottom.  Is there something I'm missing?



Again, thanks for your time.



Erik

BobC

It may be where you can't see

Erik,



If that pipe to the second floor comes up through a wall then there is probably a short (6") horizontal pipe that goes from inside the wall to where the radiator sits adjacent to the wall.



Through the years as the house settled, that pipe may have acquired a slight reverse pitch. Try shimming both ends of the radiator to raise that short pipe. I had something similar with a hall radiator in my house and used a 3/8 piece of plywood under the valve end and a 1/2" piece under the vent end, to assure positive pitch on the radiator itself..



Also make sure you check the pipe in the basement with a level, your eyes can deceive you.



Bob

jpf321

are you sure ...

are you sure the basement mains should be pitched back to the boiler .. this would describe a counter-flow system .. there is nothing at the end of the main loop that drops down towards the floor?



don't pitch the rad too much .. just enough to coax the water out in normal operation .. too much and you are pouring water into live steam and this will cause hammer ..



vent the mains fast and the rads slow .. this is an oft repeated tenet here .. probably why rads don't hammer much.



the hammering you are hearing, assuming it is not simply expansion noises, is steam picking up a bit of water and slamming it into the next solid thing, usually an elbow. your goal is to get steam and water to peacefully coexist in the same pipe .. this means not too much pitching ... our you will have a wave somewhere that will crest into the flow of steam ..

HarborAce

Pitching Problems

Hi Bob,



Thanks for the response.  I left that out of my original reply as I had forgotten about a little detail.  I thought of the short connector pipe last year and put my radiator up on 2X4's as well as some other shimming.  The radiator itself sits about 1 3/4 inches off the floor on the feed side and 2  inches off on the vent side, giving it about a quarter inch of pitch across about 16-18 inch span.  I did this after pitching just the radiator's back end.  Since the hammering continued, I assumed the piping was out of pitch.



After doing this I didn't noticed much of a change.



I did use a level to check the basement pipes, but I'm not too sure how well they're pitched.  I certainly wasn't very scientific about measure the pitch over a certain span.



I recheck the pitch in the next couple of days.  Do you think reverse pitch or too much 12-15 feet below my radiator would cause it to clang?



I appreciate you taking the time to respond.



Cheers,



Erik

HarborAce

I guess not

Hi,



I guess this is where I'm a little fuzzy about the details.  There is one pipe that leads from the larger main feed pipes.  This pipe travels about 15 feet before it rises up another 15 feet to my radiator.  It is smaller than the main pipe (I'd say an inch smaller).  The clanging seems to come from that pipe and after a couple of minutes, the clanging begins in my radiator.  I think mains are okay, or at least not bothering me as much when they clang.



The over-pitching the radiator concept intrigues me.  I'm sure part of the tenets describe what is too much pitch.  Any advice on that would be greatly appreciated.  So is the idea to not allow much, if any condensation pour back into the feed pipe while the steam is flowing?



As far as venting, I know very little about that.  My radiator's vent does seem like a lot of air gets pushed through it quickly.  It might need to be replaced in order to slow the vent process down.  Will venting a radiator too quickly lead to clanging?



I agree that it's steam hitting water.  So you're saying that by not having pitch in pipes 25-35 feet away that the hammering could manifest itself in the actual radiator (and not just as sound conductance through the pipe)?



Thanks tons for your creative input.  I look forward to hearing more.



Erik

Rod

Water Hammer

Hi Erik-

While it might sound like the water hammer is in the radiator the chances are it is in the pipe close to where it enters the radiator. Radiators act like a big drum and just amplify the noise.  Just having water in the bottom of the radiator won't cause water hammer. In the steam mains, steam travels in the upper half of the pipe and water in the lower half, normally without water hammer.



Water Hammer -Think of pouring water from a 5 gal bottle with no vent. If you pour the water slowly, the water runs out steadily and air travels into the bottle to replace the water. If you tilt the 5gal bottle so more water runs out, the bottle starts going "Glug, Glug, Glug" as the water runs out in "slugs" and air tries to rush to fill the vacuum formed by the departing water.

 Let's think about steam for a moment. Keep in mind roughly 1 cubic foot of steam collapses (condenses)  to 1 cubic inch of water. That's about 1700 to 1.  Steam collapses (condenses) instantly!

Now let's go to your radiator. The boiler starts producing steam and the steam starts entering your radiator. As the radiator is cold as soon as the steam touches the inner walls of the radiator it starts condensing like mad. More steam rushes in to fill the vacuum formed by the condensing steam.  All this condensing produces a lot of condensate (water).  At first is flows slowly but as the volume of water builds it starts acting like the pouring water from the 5 gal water bottle. It goes "Glug, Glug, Glug" which builds waves of condensate (water) in the piping. 

Now we get to the water hammer part - If steam in the pipe gets caught between these waves, it may just up and (instantly)collapse. Where steam was before is now a huge vacuum void. The waves on both sides rush in to fill the void and violently crash together making the noise we call "water hammer"!



Now we know what is happening we have to figure out how to stop it.

What is needed is to stop the "Glug, Glug, Glug" (waves) . It also helps to use insulation to keep the piping warm,

Stopping the "Glug, Glug, Glug." -

1 As Jamie mentioned- Use a bigger diameter pipe. This allows more room so the steam is less likely to get trapped between the waves. (Obviously this may not be practical)

2. Don't tilt the radiator (the 5 gal jug ) as much. You need a little bit of slope so the water will flow out the radiator, too much slope causes problems.

3. Slow down the condensing of the steam in the radiator. To do this you want to slow down the radiator's venting of air which means steam will fill the radiator more slowly. This allows the radiator to warm up slowly and produces less volume of condensate (water) leaving the radiator. You mentioned that the hammering subsides as the radiator warms up. You just need to get it to warm up more slowly.



I would try an adjustable vent on the radiator and set it at the lowest setting. A Vent-Rite #1 or a Hoffman 1A would be good vents to try. You can get Hoffman 1As at  Pex Supply on the internet.

Good luck with it. Water Hammer in the middle of the night is annoying!

- Rod

HarborAce

Maths and such

Hi Rod,



Thanks tons for your detailed reply.  I'm a computer programmer now so I really appreciate the math aspects of plumbing.



I'm going to check the pitches on my pipes, ease off on the radiator tilt, and invest in a Hoffman 1A.  Since it's not my house, I'm not too keen on repiping a feed line, so I'll have to do the best with what is installed.



Would you advise decreasing the pressure on the control from 2 lbs to 1.5 lb?  Perhaps that might slow the steam down a bit.  It does get to my radiator (which is the furthest one) fairly quickly.



Thanks again for your reply.  I'll report back soon.



Erik

jpf321

steam moves fast...

steam does move quite fast .. the lower the pressure the faster .. it's hard to wrap your head around, just take it as a truth ..



anyway, the pressure setting on the pressure control should be turned down .. in two places .. 1) the screw on the top should send the scale on the front to 0.5 .. 2) there is likely a white dial inside .. turn it down to 1 .. this is a "properly" (at least to wallies) adjusted pressure gauge for 98% of situations.



however, the system may not even build pressure to even get the pressure control involved in the scenario .. in most cases, the thermostat (if there is one) clicks off before the pressure even begins to rise significantly (at least in a reasonably constructed system on a not very cold day) .. and don't forget the setting on the pressure control doesn't "control" (increase/decrease) supply pressure .. it only sets a point where the system will shutdown (perhaps just momentarily) when the pressure reaches this point .. but the general consensus is that settings of 0.5 and 1 (1.5psi = cut-out (shutdown) and 0.5psi is cut-in (fire up)) are a good point to take a breather .. because in reailty, you don't NEED any more pressure than this to properly heat, so shut it down. you will see some of mention that we operate at less than 1psi .. i operate at 6oz as my high limit.



so anyway, my point is that it may not be a pressure issue at all .. likely it is much more a pitch issue .. at least that's an easily addressed issue. there are other situations that cause water hammer but let's eliminate pitch problems first .. i believe that a parallel flow (steam and water moving in same direction) system calls for 1inch in 20ft AWAY from the boiler and a counterflow (steam and water moving in opposite directions) calls for 1inch in 10ft TOWARDS the boiler for the mains.



you may also have a SAGGING pipe that has a slight bow to it and is holding water in the bottom. you mentioned that you raised the entire rad up onto 2x4 .. do you know if that effected any of the basement piping? perhaps you now have a RISE in the area of your rad feed "riser" where water is settleing on 1side or the other attemping to get to where it's trying to go, or you made a condition whereby the steam and water have a very small space share.



let us know.

The Steam Whisperer (Formerly Boilerpro)

Something missed.....

You mentioned the boiler water being very dirty.  This is almost guaranteed to be at least a contributing factor.  If you can, spend some time flushing, skimming and  cleaning out that boiler.  It is likely that the dirty boiler water is causing an excessive amount of water to leave the boiler with the steam, and can cause lots of water hammer.   Dirty boiler water with the typical incorrect near boiler piping can be a very noisy combination.  Getting one or the other right often restores at least some level of peace.  You may have too small a runout to the radiator (usually one size larger than the riser), but if the steam is clean it will often work anyway.  Also, make sure the pressuretrol is actually working...If not the pigtail may need cleaning.

Always keep in mind, that with steam the symptom and the problem are rarely in the same room.