The maximum distance between the anchor poles supporting a cable should not exceed 600m. If the poles are set further apart, the weight supported by the cable will not propagate all the way through to the anchor poles. This can cause the cable to deflect far more between some of the support poles than between others, adversely affecting the clearance.

The maximum distance is calculated as follows:

The maximum span between support poles is 75m (see reasons given under laterals). Water from sub-main pipes is delivered via a feeder pipe and then split in two directions into the laterals. Therefore a sub-main is needed every 150m and this becomes the maximum module. Four modules give a total of 600m which in turn is the limit that the load is properly propagated to the two anchor poles at either end of the structure.

If a field is wider than 600m then it is advisable to divide it into two or more equal portions and to install extra anchors and poles where necessary.