Friction Loss in PVC Plumbing
Tech Talk 61
The AES Technical Department set up this actual pumping system (shown at left) six different times using our SHE2.4
pump. Two elbow types and three pipe sizes were used to illustrate the importance of correct plumbing. Study the results below to understand these principles:
- Elbows vs. Sweeps
- Flow vs. Pipe Size
- Vertical Head vs. Total Dynamic Head (TDH)
- Pumping Cost vs. TDH
NOTE: Centrifugal Pumps (not self priming) perform best with flooded suction (pumps filled by gravity) as shown. The suction pipe should be nonrestrictive. To control pump’s output, put a valve on the discharge side.
Friction Loss in PVC Pipe
- From the chart at left, using gpm and pipe size, find the friction loss per 100' of pipe.
Example: 40 gpm in a 11/2" pipe = 10' loss per 100' of pipe. 40' then causes about 4' of head loss.
- Next find the friction loss caused by the fittings. Please note that the friction loss depends on the fitting diameter. A standard 1.5" elbow is equal to about 4' of pipe; long elbows, sweeps, and 45° elbows are equal to about 2' of pipe; straight through a "T", about 3' of pipe; and a 90° turn through a "T", about 9' of pipe.
Example: 40 gpm through 5 standard 1.5" elbows = 20' of pipe, which equals 2' of head loss. Add this to the pipe’s head loss and the actual vertical head height in feet to get Total Dynamic Head (TDH).
All pumps sold by AES are performance tested. It is up to you to determine which pump to purchase and how to plumb it correctly. If you need help, send us a sketch and we’ll size the pipe for you – at no charge.
NOTE: The electric energy required for a centrifugal pump usually goes down as the head pressure goes up. It is the opposite of an air compressor.
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