Selection of the correct pipe size is critical to spa jet performance. Jets generally require 40 lpm to 50 lpm to operate at 8m to 10m head pressure.
To ensure adequate flow to achieve this, both pump and pipe selection is critical. For 10 jets you need a pump that can deliver 400 lpm to 500 lpm at the spa after head loss is taken into account.
Head loss is calculated using pipe length, diameter and number of fittings for a given flow rate. If the pipe is too long, too small, or too many bends and fittings are used, the system head loss can be crippling to the operation of the spa.
Mistakes can be expensive
Underestimating the effect of using a small pipe size over a long run with concrete and landscaping added over the top, can not only be detrimental to spa operation, but also expensive to rectify as there may be no solution but to dig it all up to lay the correct pipe size.
As an example, with a flow rate of 210 lpm, 40mm Class 9 pipe has a head loss of 1.14m for every metre of pipe. By comparison, 50mm Class 9 pipe has a head loss of only 0.39m for every metre of pipe. 50mm pipe can run almost three times further for the same loss in head as 40mm pipe in this scenario.
It’s important to note that a change in flow-rate will result in substantial change to head loss. If installing an in-ground spa we recommend seeking clarification on the effect of head loss prior to installation if unsure of the calculations.
For more information contact technical support at Australian Spa Parts on 1300 736 025.