Centrifugal Pump Discharge Pipes

The pump will have a performance curve that is published by the manufacturer. The operating point is where the pump performance curve and the system characteristic curve intersect. So, with the same pump, it is a question of modifying the system characteristic to achieve a different operating point.

The right thing to do depends upon where on the curve the operation is. If the operating point is at the high head/low flow end of the curve, and the lift that the pump is being asked to achieve represents the bulk of that head, increasing the pipe diameter will make very little difference. However, as the installation cannot be seen from here, neither can the options.

Please find out the pressure drop in up stream of pump with existing size. You can use referances like CRANE. You calculate the pressure drop with 1.5 inch size. If you find much reduction in pressure drop, definitely the time will be reduced. Please provide more details on piping layout and pressure details . You will better guidance.

Based on some back-of-the-envelope calculations:

• if the lift is more than about 30m, don't change the pipe size; do something else.
• the velocity in a 3/4in pipe is around 2m/s, which is OK for liquids; do something else.

To increase flow, decrease friction. Change all elbows to long sweep elbows, or bent pipe, the larger the radius the less the friction. Use very smooth pipe, plastic is very smooth, steel is rough.

Move the pump closer to the source. If the pump can be placed below the source, it will increase flow, because suction head is reduced.

Increasing the pipe sizes will probably reduce friction.

If the pump can be placed below the source, it will not need a venturi jet, which creates suction by using pump energy. If your pump has to lift, it will need this jet, which reduces flow, though.

Purchase a second itty-bitty pump and operate it in parallel with the first.

This will cut your pumping time by about a third.

To cut the pumping time even further, increase the discharge piping to ~1.5 or 2"

Check motor current. and its maximum limit. Just by increasing pipe size, instead of reducing pumping time you may land up burning your motor with overload. Try 1" first.