Water hammer in system on start-up

Users who are viewing this thread

Don H

Member
Messages
38
Reaction score
9
Points
8
Location
Maryland
After not flowing water overnight I get a water hammer when the pump kicks in. A new pump and hardware was installed in 2018. There is a check valve in the pump, another on top of the pump and a third CV just prior to the pressure tank.

I've researched here and it seems the CV at the tank is not recommended. Could this be causing the water hammer?
 

Valveman

Cary Austin
Staff member
Messages
14,676
Reaction score
1,318
Points
113
Location
Lubbock, Texas
Website
cyclestopvalves.com
After not flowing water overnight I get a water hammer when the pump kicks in. A new pump and hardware was installed in 2018. There is a check valve in the pump, another on top of the pump and a third CV just prior to the pressure tank.

I've researched here and it seems the CV at the tank is not recommended. Could this be causing the water hammer?
Yep.
 

Valveman

Cary Austin
Staff member
Messages
14,676
Reaction score
1,318
Points
113
Location
Lubbock, Texas
Website
cyclestopvalves.com
The check valve at the tank is what causes the water hammer. But cycling on and off, which also slams the check valve(s) closed over and over is what wears them out to start with.

 

Valveman

Cary Austin
Staff member
Messages
14,676
Reaction score
1,318
Points
113
Location
Lubbock, Texas
Website
cyclestopvalves.com
Instead of just removing the guts of the CV, replace it with a CSV1A and you will have solved several other problems as well. Just so happens the place where that second check valve should not be, is usually the perfect place and length to install a Cycle Stop Valve.

 

2stupid2fixit

Active Member
Messages
137
Reaction score
39
Points
28
Location
Penn Forest Township, Pennsylvania
You solved the problem by removing the extra check valve. I studied the physics behind this and multiple check valves along the same line will only fight for equilibrium... vacuum forces at play. In any well setup, its an unnecessary battle. You want the pump to push water to its final place of use. Check valves after the pump will only create air gaps, which make sputtering and water hammer. Even the most perfectly installed systems will have some point to let in air, which can only make headaches.
 

Sarg

Enjoy Learning
Messages
229
Reaction score
51
Points
28
Location
Upstate New York
Just as Valveman suggests.

CSV1A.JPG
 

Valveman

Cary Austin
Staff member
Messages
14,676
Reaction score
1,318
Points
113
Location
Lubbock, Texas
Website
cyclestopvalves.com
You solved the problem by removing the extra check valve. I studied the physics behind this and multiple check valves along the same line will only fight for equilibrium... vacuum forces at play. In any well setup, its an unnecessary battle. You want the pump to push water to its final place of use. Check valves after the pump will only create air gaps, which make sputtering and water hammer. Even the most perfectly installed systems will have some point to let in air, which can only make headaches.
Exactly! Now you only have the problem of the one check valve on the pump that is needed slamming shut from the wide open position every time the pump stops. Adding a CSV makes the tank fill at 1 GPM, which means the check valve is also in the 1 GPM position or only open about as much as the thickness of a piece of paper when the pump shuts off. This mechanical soft stop from the CSV eliminates the water hammer as well as damage to the check valve.
 
Top
Hey, wait a minute.

This is awkward, but...

It looks like you're using an ad blocker. We get it, but (1) terrylove.com can't live without ads, and (2) ad blockers can cause issues with videos and comments. If you'd like to support the site, please allow ads.

If any particular ad is your REASON for blocking ads, please let us know. We might be able to do something about it. Thanks.
I've Disabled AdBlock    No Thanks