# Toliet flush cause pipe bang noise



## LadyGunner (Jan 14, 2009)

a couple of weeks ago - every so often when a toilet was flushed in my house the pipes will make a knock/bang noise.  I have 2 bathrooms - the other does it too.

today I climbed up on the roof to make sure there wasn't  big bird or something sitting on the vent pipe.  nothing.  there is a stank coming out of the vent pipe pheww!

When I flush the toilets if I hold the chain & flapper piece up till all the water goes out - it usually will not bang

does this mean the guts of these toilets are bad?
they are both very old

any ideas is appreciated
thank you


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## contender* (Jan 14, 2009)

Don't have the answer for the banging, my upstairs one does it. I do know that the vent pipe is bound to stink....


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## 2tines (Jan 14, 2009)

probabley not your toilet at all. maybe your pipes under the floor( im guessing you do not have a concrete floor)


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## LadyGunner (Jan 14, 2009)

2tines said:


> probabley not your toilet at all. maybe your pipes under the floor( im guessing you do not have a concrete floor)



no concrete floor, Its plywood with laminate over it. I have a split level - all living up stairs - then under the floor is garage area & finished room.  

pipes in ceiling of garage are exposed - there's no ceiling. only insulation I stuffed up there

any troubleshooting I can try to find a solution?


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## Twenty five ought six (Jan 14, 2009)

You have water hammer.

If it just started, it probably means the pipes feeding the toilet have come lose (if they were ever fastened).  What happens is that when you flush, the toilet begins filling up rapidly.  This can set up shock waves that cause the water pipe to beat against the joists or whatever else it is that it hits.  Think snapping a water hose.  That's why when you hold the flapper open, there is no hammer, because the pressure is being absorbed by the tank, which operates as a big shock absorber.

Not an uncommon problem with lazy plumbers.

You can get clamps that will clamp the pipe to each joist.  Try that and see what happens.

You also may need to add an air chamber, but as the noise is of recent origin I doubt it.  Doing that is beyond the scope of this discussion.


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## Branchminnow (Jan 14, 2009)

do what 2506 said but also if your house has any age on it at all, then your pressure reducing valve is worn out.


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## LadyGunner (Jan 14, 2009)

Thanks ya'll
I will get some clamps & start with that

Better than plan A which was a hammer & duct tape 

the house is just about 21 yrs old. is the pressure reducing valve the valve I see on my main water pipe where it comes in the house?

We just had a pressure tank installed last yr when a new water heater was installed - can that have anything to do with it?


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## jbi1104 (Jan 14, 2009)

Not a pressure tank, rather that tank is a thermal expansion device.  The majority of plumbers do not realize those tanks come set at a certain pressure to meet airline guidelines to be flown during shipment.  They need to be charged to your line pressure to work properly.  An easy fix with your standard bike pump.  There is a valve stem on the tank to add air to the tank.  

     First you will need to verify your line pressure.  A tell tell gauge made by Watts can be bought at Home depot or the like.  These have a red line that when moved by pressure, remains at the highest reading.  They screw onto a hose bibb for testing purposes.  I recommend using the rear hose bibb, as the front ones are sometimes piped hot to the house for increased pressure for washing vehicles and the like.  

     If the 'pressure tank' (thermal expansion device) is not charged properly, then thermal expansion could result in a closed system such as yours, and yes thermal expansion can rattles pipes mimicking water hammer.   

     Water Hammer could be the likely culprit.  An easy fix of sorts is to buy a Sioux Chief or the like water hammer arrestor and place it at your washing machine box.  They make them to screw onto the existing valves, since most homeowners can not solder and are unwilling to cut their lines to put one in place.  This may correct the problem.  

     Does your house only have 1 vent through the roof or are there more than 1?  A lot of houses are being built using one main vent and using Air Admittance Valves for the remaining fixtures.  While these devices work alright, they do go bad over time and need to be replaced. 



LadyGunner said:


> Thanks ya'll
> I will get some clamps & start with that
> 
> Better than plan A which was a hammer & duct tape
> ...


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## BigTime (Jan 15, 2009)

Try taking a stool softner!!


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## jason4445 (Jan 15, 2009)

Water Hammer I had it.  When you turn a faucet off quickly it sets up a shock wave that travels through the pipes.  To off set this intake water system ( in older houses) usually have a extra length of pipe above where the intake line comes through the wall to the faucet.  When the water system is full air is trapped in this extended section to act as a buffer for the shock wave.  Over time the air is lost and water fills this extension and there is no longer an air buffer.

To fix this you should drain all water from both the hot and cold lines.  The easiest way is though the hot water heater.  Usually it is in the lowest part of the house like a basement.  If not this won't work. Turn off the power and the cold water intake line to the house, drain the tank until all water quits flowing.  After the tank empties the lines will drain.  Then seal the tank and turn on the intake water.  This will reestablish the air buffer in the extended sections of the lines.

Like the others said in newer homes they put some sort of tank or attachment on the lines and not extended sections.


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## Branchminnow (Jan 15, 2009)

LadyGunner said:


> We just had a pressure tank installed last yr when a new water heater was installed - can that have anything to do with it?


One more thing thermal expansion will   cause noise, but  with the tank installed it will not cause any noise thats what the Thermal expansion tank is for.  That being said.....go get a pressure reducing valve...that is your problem in light of the thermal expansion tank being installed. JMHO

you have to much pressure and your Pressure regulator is bad.


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## LadyGunner (Jan 15, 2009)

The pressure regulator HAS been making weird sounds - it comes in the wall in a finished room/ office in the basement.  

I've seen them at home depot and will do that
still plan to check pipes to make sure they have clamps holding them to my ceiling 

I truly appreciate all the advice
will post updates


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## letsgohuntin (Jan 19, 2009)

I had the same problem and installed a water hammer arrestor from Lowes. It installed easily on the water pipe going into the toilet and it took care of the problem! 

http://www.lowes.com/lowes/lkn?action=productDetail&productId=24697-1816-10662


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## LadyGunner (Jan 22, 2009)

update  - we replaced the pressure regulator valve on the main water pipe that comes in to the house.

problem solved  

thank you!


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