# D.W. shock stop



## moonapprentice (Aug 23, 2012)

Do you:

Hammer arrestor for dishwasher upstream of shut off valve.

Or 

Hammer arrestor for dishwasher downstream of shut off valve in line style.


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## Plumbducky (Jun 12, 2010)

I install it right on the shut off valve

Sent from my XT1254 using Tapatalk


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## wyrickmech (Mar 16, 2013)

Hammer arrestors are to be placed as close to the source of the shock wave. The best place is at the first fitting ,so that the shock wave is absorbed into the arrestors


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## rwh (Dec 17, 2014)

Doesn't matter much. Solenoid and hammer g


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## KoleckeINC (Oct 22, 2011)

I've never put an arrestor in. 12" air chambers here. I heard from RJPHD that the arrestors get logged with water and the spring refuses to move. Then you replace them. And air chambers are forever.


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## celtic1 (Dec 16, 2008)

12 " air chamber in wall on all valves 1/2 " Dia 18 " on 3/4 " Dia


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## dclarke (Dec 22, 2012)

How exactly will an air chamber work ? If at all it would be temporary. Over a short time it would completely full with water. A proper hammer arrester at least keeps the air separated from the water. I have personally never used either method.


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## ShtRnsdownhill (Jan 13, 2016)

I gota agree with dc on not using either , if the house has a rpz on the main, then there should be an expansion tank already, and if there are any problems you can put in an arrestor in the future, but if all the piping is secured hammer usually is not an issue..again this may be a regional issue due to the different water supply systems around the country..


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## moonapprentice (Aug 23, 2012)

Hammer arrestors getting water logged through bad on ring seal over time, yes. What do think about this about air chambers


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## ShtRnsdownhill (Jan 13, 2016)

air over time diffuses into water, so unless you can recharge the air chamber, its a waste of time, thats why they went from the big steel expansion tanks on heating systems to the bladder expansion tanks with an air valve..for that reason and better control due to different pressures in systems..


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## celtic1 (Dec 16, 2008)

dclarke said:


> How exactly will an air chamber work ? If at all it would be temporary. Over a short time it would completely full with water. A proper hammer arrester at least keeps the air separated from the water. I have personally never used either method.


It's in our code. Won't pass rough without them!


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## celtic1 (Dec 16, 2008)

*There in our code*



moonapprentice said:


> Hammer arrestors getting water logged through bad on ring seal over time, yes. What do think about this about air chambers


 Won't pass rough without them ! Yes I'm well aware the eventually fill with water.
every few years drain down the home.


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## dclarke (Dec 22, 2012)

celtic1 said:


> It's in our code. Won't pass rough without them!


 guess you do what is required even when you don't agree.


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## KoleckeINC (Oct 22, 2011)

I was trying to lure RJ out of hiding. I guess he's gone forever.


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## rjbphd (Feb 5, 2010)

ShtRnsdownhill said:


> air over time diffuses into water, so unless you can recharge the air chamber, its a waste of time, thats why they went from the big steel expansion tanks on heating systems to the bladder expansion tanks with an air valve..for that reason and better control due to different pressures in systems..


Late Comer here, that's one of the biggest crock I've read here... reason for steel tank get water logged, improper tank fittings and improper pump location on the system.


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## rjbphd (Feb 5, 2010)

KoleckeINC said:


> I was trying to lure RJ out of hiding. I guess he's gone forever.


Found my way back... those 12" dead end pipe used for air chamber are useless like ties on men after three weeks of use..


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## ShtRnsdownhill (Jan 13, 2016)

rjbphd said:


> Late Comer here, that's one of the biggest crock I've read here... reason for steel tank get water logged, improper tank fittings and improper pump location on the system.


if the steel tanks where so good, why arent they used anymore?...


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## KoleckeINC (Oct 22, 2011)

That's why I like you RJ-your not afraid to speak your mind no matter how wrong you are. Pre charged air chambers get recycled into scrap in the country of Chicago


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## rjbphd (Feb 5, 2010)

ShtRnsdownhill said:


> if the steel tanks where so good, why arent they used anymore?...


Because they don't know anything about it.. did a 1938 boiler job replacement ( nicor sponsored company scared this lady about cracked heating exchanger, asked her wheres the water on floor if cracked, but she want it replaced), the steel riveted tank had both proper tank fitting on it and wasn't water logged so I re used it.


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## GAN (Jul 10, 2012)

Air chambers or arrestors at the end of long runs or fast closing jobs here in Illinois.

Usually see air chambers on residential & small commercial jobs. Arrestors on larger commercial work.

Agree they do get water logged, but a simple drain down will let them recharge.

Compression of air on the end of a long run can be ten fold the static water pressure.

*Section 890.1210 Design of a Building Water Distribution System* 


f) Water Hammer. All building water supply systems shall be provided with air chambers or approved mechanical devices or water hammer arrestors to absorb pressure surges. Water pressure absorbers shall be installed at the ends of long pipe runs or near batteries of fixtures. 

1) Air Chambers − An air chamber that is installed in a fixture supply shall be at least 12 inches in length and the same diameter as the fixture supply, or an air chamber with an equivalent volume may be used. An air chamber that is installed in a riser shall be at least 24 inches in length and at least the same size as the riser. 

2) Mechanical Devices − If a mechanical device or water hammer arrestor is used, the manufacturer's specifications for location and installation shall be followed.


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## ShtRnsdownhill (Jan 13, 2016)

rjbphd said:


> Because they don't know anything about it.. did a 1938 boiler job replacement ( nicor sponsored company scared this lady about cracked heating exchanger, asked her wheres the water on floor if cracked, but she want it replaced), the steel riveted tank had both proper tank fitting on it and wasn't water logged so I re used it.


who is " they".. are you referring to plumbers?


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## ShtRnsdownhill (Jan 13, 2016)

Air in system: Air can cause knocking and hammering noises inside a boiler when it fires. While this is more annoying than harmful, entrained air also acts as an insulator and will lower boiler efficiency. It is therefore important to eliminate air from the system. In compression expansion tanks, air is in direct contact with the water. In Bladder/Diaphragm tanks the air is not in direct contact with the water. Why is this important? Because when the system cools down the volume of water will shrink. Furthermore if the water is in direct contact with air it will absorb more air as it gets cooler. In systems with compression tanks, this air can get back into the main piping and work its way back through the boiler until it reaches the air separator where it will separate out and follow the piping back up to the expansion tank where it belongs. Do not put automatic air vents on systems with compression tanks as eliminating this air will eventually reduce the air volume in the tank until it isn’t enough to be effective or becomes waterlogged. Gauge glass seals and valve packings on compression tanks may also be a slow escape path for air and eventually cause the tank to lose its air cushion. System connection to a compression tank should always be with a B&G Airtrol Fitting which acts like a trap to help keep air in the tank. If the system stays hot all the time then the shrinkage and air getting back into the system will not happen. Systems using compression tanks are called air control systems. 
Systems using Bladder/Diaphragm tanks are called air elimination or air removal systems. This system uses air separators and manual or automatic air vents to get rid of air in the system. 

so the reason air disappears from the metal expansion tank is the cooler water lets more air diffuse into the water..not from pump placement..as new boilers today are mostly cold start this will be a problem and hence the use of bladder type expansion tanks...if you want to read the whole article.. http://www.riteboiler.com/expansion-tanks.php


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## rjbphd (Feb 5, 2010)

ShtRnsdownhill said:


> Air in system: Air can cause knocking and hammering noises inside a boiler when it fires. While this is more annoying than harmful, entrained air also acts as an insulator and will lower boiler efficiency. It is therefore important to eliminate air from the system. In compression expansion tanks, air is in direct contact with the water. In Bladder/Diaphragm tanks the air is not in direct contact with the water. Why is this important? Because when the system cools down the volume of water will shrink. Furthermore if the water is in direct contact with air it will absorb more air as it gets cooler. In systems with compression tanks, this air can get back into the main piping and work its way back through the boiler until it reaches the air separator where it will separate out and follow the piping back up to the expansion tank where it belongs. Do not put automatic air vents on systems with compression tanks as eliminating this air will eventually reduce the air volume in the tank until it isn’t enough to be effective or becomes waterlogged. Gauge glass seals and valve packings on compression tanks may also be a slow escape path for air and eventually cause the tank to lose its air cushion. System connection to a compression tank should always be with a B&G Airtrol Fitting which acts like a trap to help keep air in the tank. If the system stays hot all the time then the shrinkage and air getting back into the system will not happen. Systems using compression tanks are called air control systems.
> Systems using Bladder/Diaphragm tanks are called air elimination or air removal systems. This system uses air separators and manual or automatic air vents to get rid of air in the system.
> 
> so the reason air disappears from the metal expansion tank is the cooler water lets more air diffuse into the water..not from pump placement..as new boilers today are mostly cold start this will be a problem and hence the use of bladder type expansion tanks...if you want to read the whole article.. http://www.riteboiler.com/expansion-tanks.php


Don't need air seperator if the boiler is piped properly


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