Installation manual

4.7.1. Pipe sizes

Pipe sizes commonly used with our hydro products include:

 PVC for larger sizes based on OD (110-300 mm normally)

 MDPE or HDPE based on OD (50-110 mm normally)

 LDPE based on ID in NZ/AUS (40-50 mm normally)

Many different standards exist for pipe sizes which vary depending on industry and

geographical area. The pipe size designation normally includes two numbers - one that

indicates the outside diameter (OD) and the other that indicates the wall thickness. American

pipes were categorized by inside diameter (ID) in the past but this was abandoned to

improve compatibility with pipe fittings and joiners that usually fit the OD of the pipe.

Inside diameter is critical for calculation of pipe friction loss since a variation of as little as

1 mm can have a very significant effect on the output power of the turbine. Take care with

which diameter you are referring to since if calculations are done based on pipe ID and the

pipe is then purchased based on OD your turbine will generate less power than predicted

due to increased pipe friction. Pipes below 40 mm ID cannot normally be used as friction

losses are too high.

Pipes have different pressure ratings so a given pipe size is often available in a number of

pressure ratings. These different ratings are achieved by either altering the material grade

(Low, Medium or High Density PE) or increasing the pipe wall thickness. The OD is kept

constant so standard pipe joiners still fit.

In NZ for example, polyethylene (PE) pipes can be purchased from 35 m (50 psi) head rating

to 160 m (230 psi) head rating. Some sizes are based on ID but most are based on OD

sizing, so be careful and double check with your supplier the OD and ID of the pipe.

4.7.2. Pipe material

A pipe should be:

 Equal to or larger than recommended from the calculations that specified the output

power (Watts) of your turbine.

 Cost effective, tough and durable for 20-50 years.

 Able to handle the static pressure of the head of water.

 Able to handle the running head x a factor 1.5 to allow for water hammer

 Easy to lay and bend around obstacles.

 Able to be purchased in long lengths.

The PowerSpout PLT has a maximum running head rating of 130 m and allowing for up to

25% pipe friction loss, sites up to 160 m static head can be used. A higher water head can

be used successfully but with reduced lifespan and warranty.

4.7.3. MDPE and HDPE pipes

The range and the fact that they are durable, low cost and commonly available in a wide

range of sizes, pressure ratings and lengths makes PE pipes the obvious choice for the

PowerSpout PLT turbines.

Remember that you can vary the pipe pressure rating to minimise costs. For example, if you

have a 100 m head you start with low grade (50 psi, 3.5 bar) pipe, a length of 6 bar, then 9

bar and finally 12 bar. Laying 12 bar pipe all the way would almost double the cost of the

pipeline. If you do this the pipe ID will change, so the calculated output may not be correct.

To avoid disappointment use the smallest pipe ID in the online calculator and your turbine

should generate a little more than predicted.