Flow Through Pipe

The flow in the existing system can be increased by

Getting the pump to turn faster (with more HP required) or

Reducing the friction somewhere by increasing the pipe size or add a second pipe. (also more HP) or

Add a booster pump in the line.

A smaller flow can be achieved by throttling the discharge. (using less HP) (note the HP is calculated from Q * pressure at the pump)

Greetings.

250 GPM through a 4" pipe is only a small part of the pipe's capacity. Do you think that flow would increase if brought larger?

Throttling the discharge would reduce flow, and raise discharge pressure. Still requiring about the same HP. I think.

The only efficient way to reduce flow is to slow the pump.

Bob c is right 250GPM is rater small for 4" but if the line is long enough it will make a difference.

In a Centrifugal pump closing the discharge valve will reduce the HP. A positive displacement pump should however not be not be controlled by a valve.

The correct answer will depend on what you have.

What type of pump are you using?

Do you have a variable speed drive?

What are you pumping?

It sounds like 250 gpm is target flow for conditions when flows are throttled, and X gpm is maximum flow with all valve wide open?

First step is to review the selected pump flow curve. Throttled flow gives a pressure point on this curve. Unthrottled flow will have a lower system pressure and result in higher flow rate.

Based on higher flow rate, the system curve will change. Depending on the system complexity, do you want to calculate the Min/Max flow rate, or can you install the pump in the system and determine it experimentally?

As stated in other answers, what type of pump is it? Need to calculate velocity also to determine pipe size needed at max flow rate, which, as asked previously, what are you pumping, as that will also figure into calculating velocity.

Q/A = V