Supposed that each pump in the system is identical, check the NPSHa of the suction piping per maximum flow condition of two combined groups, which need to meet the NPSHr of each pump.

Q: Is it correct the discharge pipe size same as the suction pipe? Is the pipe sizing met pump hydraulic requirements?

The pumps in the same group are similar each other. Pumps in different group have different flow rate and head. Delivery manifold is oversized to 10".

No pump is equal to another. With three in parallel you need some way to trim each pump to get equal flow.

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I don't see any significant problems provided NPSHa at each pump is correct during operation. However, without a complete breakdown on pump performance and the installation it's guess work.

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.)

Hello Hartur0,

I have seen enough balancing problems of parallell pumps to raise a warning finger! It might turn out as a smooth operation at first try, but:

If two or more identical pumps in parallell shall perform equally, eg. pump equal amount of liquid, they must have equal amount and pressure of liquid at intake. This could easily differ by a single line (even somewhat oversized) feeding a row of intakes. First and second intake might dominate.

The same problem might occur at output side. First pump might dominate, giving a full pipe and pressure and the other pumps less.

To avoid feeding problems, skew loads of pumps and hammering problems: correct sizing of pumps and piping, regulating possibillities, correct piping layout and design, correct type (softclosing!) and placement of checkvalves, correct outlet (ending) of pipes, air outlet and vacuum protection valves correctly sized and placed.


Good luck!

You have a 10" feeding into the header, then a 10" to the first group and 10" pipe to the other 4-pump group? I foresee balancing problems and one pump/group trying to "steal" water from the other.

To balance out the flows on the set of 3+1 pumps,connect the discharge header to the end where the last pump is - you've now got the discharge header coming off the opposite end, at the first pump. Also beware of line hammer if you are planning to autostart the standby pump.