Water Hammer Arrestor on hot water line 5

[DrClassic]

Is it of any use to install water hammer arrestor on hot water line .My project consists of housing rooms with 50 liters electric water heaters .the owner requested WHA on both cold ends and hot ends . You know that Water Heater adds about 0.5 bar pressure loss to the circuit , so methinks it will work as a pressure attenuator .Does anybody think it fit on hot line other than Automatic Washing Machine .

 

[BigInch]

A water heater may or may not help waterhammer. If you think waterhammer may be a problem, you should first try to reduce the velocity of the water to less than 3m/s by increasing pipe diameter. What pipe diameter do you need to keep velocities below 3m/s?

 

[PEDARRIN2]

Putting water hammer arrestors on the hot water to a washing machine or to a dishwasher is common practice due to the solenoid valve. Also, adding better support helps. Often in residential type construction, pipe supports are somewhat lax.

 

[BigInch]

A little extra pipe diameter doesn't cost as much as would a lot of pipe supports and surge valves for a small, relatively technically undemanding system. If you were talking a few km of high strength alloy, high pressure, high temperature, piping, OK, use small diameter and go for high velocity piping with a surge valve at each washing machine. Just don't do it here.

 

[LittleInch]

Is it of any use?

Only if you get water hammer.

The heater might act as a form of attenuator.

for a multi room / building, you normally get enough attenuation with multiple users.

If they are simple and cheap, put them in.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Compositepro]

Residential hot water lines are often kept small to minimize heat losses. In larger pipe you have to drain a lot more water before it gets hot at the tap and all the residual hot water will loose its heat before the next use.
The water heater tank has almost no damping effect on downstream piping.

 

[sailoday28]

Referring toPEDARRIN2 (Mechanical)post.
It is how fast or slow the valve opens.

 

[PEDARRIN2]

http://www.oatey.com/products/supply-boxes/washing-machine-outlet-boxes/quadtro-viega-pex-press

 

[Artisi]

Does the cost of an arrestor outweigh the risk of a pipe failure?

It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)

 

[3DDave]

Water hammer is from trying to make a sudden change in the momentum of the water. Within reason it doesn't matter what temperature the water is, it matters how much water and how big the momentum change is. I doubt that there is a chance of pipe failure in this case, but the rattling that happens when the pipe supports get loose over time can be annoying.

 

[DrClassic]

Thanx to BigInch ,PEDARRIN2 , LittleInch , Compositepro , sailoday28 , PEDARRIN2 , Artisi , 3DDave for your valuable replies.
The system is a pressurized one ; water is pumped directly to buildings . Also it is a housing project of not less than 300 toilets .
The said project will be done in say 13 cities so when it is possible to save 25$ , this sum will be about 100,000$.
My point was that water going to water heater undergoes pressure drop in two angle valves and a check valve and two hoses .Also it was a common complain that hot water was not OK for low buildings with overhead tanks .

 

[BigInch]

At high velocities it is possible to generate surges that reach 1.5 x operating pressure, so it goes without saying that failures are possible. The noise can be very annoying. Keep the velocities below 2m/s and you will probably be fine in most cases.

The problem with trying to use heaters by themselves as surge devices is that they let water out equally as fast as they let it in, just a little bit later.

 

[bimr]

While it is true that water heaters may be damaged by water hammer, putting the water hammer arrestors on the water heater will not help as the water hammer does not originate at the water heater.

Install the water hammer arrester at the end of the branch line within 6 feet of the last fixture served. The fixture is where the water hammer originates.

Please refer to the upload.