Pumps in Parallel

[remp]

If 2 pumps different sizes are pumping into a common manifold will there be a problem?. Will the larger pump's discharge pressure shut off the non retrun valve on the other pump if it is too big causing the smaller pump to do nothing just spin?

 

[willard3]

http://www.bellgossett.com/Press/BG-unparallel.asp

 

[lurch17]

No problem Remp, as long as both pumps are actually pumping at all system operating points - I do it all the time with pumps in the 20 to 75 HP range. One system I designed has a 10Hp, 20HP, and 40HP in parallel - works great.

Some considerations:
Each pump's motor must handle the pump over its entire curve, for that day when the sister pump breaks down - you still want some flow, even if not full. If the motor is not large enough to handle the end of the curve, it will trip out and you have no flow.
If these are pumps you already have, you may have to trim the impeller on one of them - or buy a bigger impeller (expensive).

 

[Ziggypump]

As long as the smaller pump is able to pump at a pressure high enough to keep water to force open the check valve, then there will be no problems with dead heading your pump. A pump can have a lower flow rate than the other pump, but it still needs to be able to achieve the appropriate head required for the system.