Banging Pipes


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Old 02-21-15, 09:07 AM
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Banging Pipes

Good morning,

We have 2 zone baseboard heating between the first floor and the basement. I have noticed that almost instantaneously with the thermostat clicking on there is a loud banging noise in the pipes. It does not happen every time but I would say at least 25% of the time. This is especially alarming in the middle of the night when it sounds like the house is going to explode.

We have an expansion tank that is appr. 1 year old (Home Depot). A friend with some plumbing knowledge came over last week and unscrewed it to see if it was filled with water. It had some water but not filled. He also pressed the valve on the back of the tank and heard the hiss. He said there is pressure in there and so the tank is good.

I have tried bleeding the pipes multiple times by just running the spout that comes off the furnace (white hose in pics) for a while but there is little gas left in the pipes. And yet the pipes keep banging.

My questions are:

Am I bleeding the pipes correctly?
Does the fact that there is pressurized air in the expansion tank enough to call it OK?

Any advice would be greatly appreciated. Thank you in advance for your help and advice.
 
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Old 02-21-15, 09:38 AM
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The same plumber that installed your system must have installed my friends. Pressure tank upside down, air bleeder in a 99% useless location. No actual air purge system.

When you tested the pressure in your tank you probably let most of the air out. You have to pressurize that tank when the main system is at 0psi. It only takes a tiny pocket of air. A bike tire pump is all you need.

Not sure why the pipes are banging. I'll defer to the more knowledgeable as this isn't my forum.
 
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Old 02-21-15, 09:51 AM
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It had some water but not filled. He also pressed the valve on the back of the tank and heard the hiss. He said there is pressure in there and so the tank is good.
Let's start with this then...

As PJ has said, he probably let out too much air and dropped the correct charge on the tank even more than it was, and it probably was already low.

"... there is pressure ..." OK, HOW MUCH? Is it the correct amount of pressure?

Does the fact that there is pressurized air in the expansion tank enough to call it OK?
No, it is not. It must be the correct pressure.

If the tank were removed and there was still water inside, then there's some problem with that tank. A tank that is removed and pressurized to the correct air charge (i.e. 12-15 PSI) should not retain ANY water at all.

You need to read this:

http://www.doityourself.com/forum/bo...sion-tank.html
 

Last edited by NJT; 02-21-15 at 10:13 AM.
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Old 02-21-15, 09:56 AM
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And yes, that tank is improperly installed... but it will still work that way... it's not right though ... it will collect air inside the water side of the diaphragm and ultimately this will cause premature tank failure.

It's good that a valve was installed... but even better would have been a valve and then a DRAIN VALVE between the shutoff and the tank. This would make it unnecessary to remove the tank in order to properly adjust the air charge in the tank. You could hook a hose to the drain, close the shutoff and isolate the tank from the system, open the drain and expose the water side of the tank to atmospheric pressure, check and adjust the air, and then simply close the drain and open the shutoff and you're back in business... read those threads in previous post... explains it all in more detail.
 
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Old 02-21-15, 10:11 AM
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Am I bleeding the pipes correctly?
No, probably not.

If you did not shut the boiler down, allow it to cool to 100F or LESS, and CLOSE THAT YELLOW valve below the drain with the hose, you never had any water flow through the zone at all. The water will take the path of least resistance and go into the boiler, up past the pump, and out the drain... never going into the zone. The yellow valve is a 'roadblock' that forces the water to take the longer detour through the zone before going out the drain.

There should be a similar valve setup on the OTHER pipe coming off that branch above the pump, is there? I think I can see one peeking out behind the tank... you should also close that one. If you want to bleed both branches you need to do the same thing for both.

But it's not likely that air in the pipes will cause a banging loud enough to wake you... it doesn't sound like the problem to me.
 
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Old 02-21-15, 10:17 AM
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We have 2 zone baseboard heating between the first floor and the basement. I have noticed that almost instantaneously with the thermostat clicking on there is a loud banging noise in the pipes. It does not happen every time but I would say at least 25% of the time. This is especially alarming in the middle of the night when it sounds like the house is going to explode.
What you describe here sounds to me like WATER HAMMER, and NOTHING to do with air in the system.

You have 2 zones you say... meaning that you have 2 thermostats... and that you must have ELECTRIC ZONE VALVES. I don't see them in the pictures, can you show us the rest of the piping please? MORE PICS, of EVERYTHING related to the boiler in the basement.

instantaneously with the thermostat clicking on
Are you sure that it is not occurring when the thermostat is clicking OFF ?

it sounds like the house is going to explode
This is NOT an issue with air in the system.
 
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Old 02-21-15, 10:20 AM
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I would also like to refer you to this information:

http://www.doityourself.com/forum/bo...ure-gauge.html

And would like you to tell us the pressure and temperature readings on the existing boiler gauge. A close up picture might be better.
 
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Old 02-21-15, 11:20 AM
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Thank you all for your advice.

It is possible that the noise occurs when the thermostat shuts "off" rather than "on".

I have attached more pics.

Thank you very much.
 
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Old 02-21-15, 11:30 AM
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In the following picture I believe that what I see is an arrow on the left hand zone valve pointing in the UP direction. Is that correct?

These pipes are on the RETURN back to the boiler and the water flow is DOWN.

Is the OTHER valve also pointing UP?

It would seem that whomever installed this system interpreted those arrows as to mean that the valve should be installed that way, and that is WRONG.

Those arrows are to show the proper direction of water flow through the valve and if that is in fact the return to the boiler from the radiators (it is) then those valves are installed UPSIDE DOWN and it is absolutely the reason for the banging.

They need to be reversed.

 
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Old 02-21-15, 11:34 AM
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Are you the OWNER of this building?

It appears to me by the multiple water heaters that it is a multi-family home.

If you are NOT the OWNER, then you must NOT be doing anything to that system. You don't own it.

Call the landlord.
 
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Old 02-21-15, 12:00 PM
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Yes...it is a 2 family house and I am the owner.
 
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Old 02-21-15, 12:11 PM
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OK, then you know what you need to do...

Reverse the direction of the zone valves so the arrows point in the direction of the flow

Properly recharge the expansion tank.
 
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Old 02-21-15, 06:32 PM
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Thank you. But I think the arrows are pointing in the right direction.
 
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Old 02-21-15, 06:46 PM
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But I think the arrows are pointing in the right direction.
You do?

Am I seeing it wrong in the photo? Are the arrows NOT pointing UP ?

Can you take a close up of the valve showing the arrow pointing DOWN please?

Isn't the pump that moves your water down at the bottom of the boiler and pumping INTO the boiler?

Isn't the water flow in those pipes going DOWN?
 
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Old 02-21-15, 06:52 PM
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Maybe you've got the system pump installed upside down then, if you think the flow should come out of the boiler at the bottom and in at the top?

Take a clear shot of the pump that we can see which direction IT is pumping.
 
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Old 02-22-15, 06:45 AM
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My apologies. You are absolutely correct. They are indeed pointing in the opposite direction. Could this be cause of the banging? And if yes, how?

Thank you again.
 
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Old 02-22-15, 09:50 AM
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Could this be cause of the banging? And if yes, how?
Absolutely, 100%.

The design of those valves is such that if they are installed backward when they close they will SLAM SHUT from the force of the water flow.

Inside is a composite rubber ball that is pushed against the pipe opening.

When installed in the correct direction, that ball is being pushed AGAINST the flow. It CAN'T slam shut because it's pushing against the water flow.

In the wrong direction, that ball is closing WITH the flow. The water SLAMS it shut.

What you are hearing when that valve closes is called WATER HAMMER. Because the water is in motion and can't stop on a dime, it creates a 'shock wave' through the piping when the valve slams shut.
 
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Old 02-22-15, 07:33 PM
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So it looks like the the pipe coming out of the boiler, going through the pump, and leading to the 2 zone valves is the hot water for the baseboard heaters. And if that is true then the arrows on the vales are pointing in the right direction...maybe. Am I understanding that correctly? But it also looks like the arrow on the pump is in the opposite direction.

I am attaching 2 pics of the pump. I also attached a picture of the return pipe which the plumber labeled.

Again, thank you very much in advance for your help.
 
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Old 02-22-15, 07:43 PM
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So it looks like the the pipe coming out of the boiler, going through the pump, and leading to the 2 zone valves is the hot water for the baseboard heaters. And if that is true then the arrows on the vales are pointing in the right direction...maybe. Am I understanding that correctly? But it also looks like the arrow on the pump is in the opposite direction.
The pipe on the TOP of the boiler, in front of the flue pipe is the SUPPLY OUT of the boiler going TO the baseboards. The flow in this pipe is UP toward the ceiling.

The pump is in fact installed in the correct direction, it is pumping INTO the boiler, the RETURN water coming FROM the baseboards.

The water flow direction in the return pipes is DOWN , TOWARD the boiler.

The flow through a boiler is ALWAYS going IN on the bottom, and OUT on the top.

If the arrows on the zone valves are pointing UP, they are BACKWARDS.
 
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Old 02-22-15, 08:37 PM
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I see. Thank you.

So in that case, should the zone valves have been installed on the pipes heading out of the furnace to the baseboards. Or are they OK on the return pipes?
 
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Old 02-22-15, 09:57 PM
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U,
They can go on supply or return but must be facing the right direction.
If yours are on the same line as the pump the arrows should be facing the pump because it's on the return.
 
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Old 02-23-15, 10:12 AM
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Q: So in that case, should the zone valves have been installed on the pipes heading out of the furnace to the baseboards. Or are they OK on the return pipes?
A: Zone valves located on the return, is optimal.
 
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Old 02-23-15, 02:07 PM
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One more question. Is the expansion tank in the wrong place? Should it placed on the hot water supply pipes to the baseboards?
 
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Old 02-23-15, 03:46 PM
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Is the expansion tank in the wrong place?
Yes and No.

If you do not have continual problems with air in the system, it's fine right where it is.

It IS upside down from manufacturers recommendation, but it will still work, just might not last as long... or it might last forever (IF you maintain the air charge BI-ANNUALLY).

There are MILLIONS of systems out there with the tank the 'technically' wrong location AND upside down that work perfectly fine.

Why do you want to make work for yourself?
 
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Old 03-03-15, 09:26 AM
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I just wanted to thank you all for the advice. The plumber reversed the valves and the banging stopped. Thanks again.

Andy
 
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Old 03-03-15, 11:40 AM
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Hi Andy, good news! Now you can get some sleep... thanks for letting us know!
 
 

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