· Michael Blair
Irrigation is usually the largest variable component of a Nashville summer water bill, and it is also where leaks hide, because the system runs at night when nobody is watching.
Normal versus abnormal
A lawn taking an inch a week over a typical suburban lot uses a substantial volume, and a summer bill several times the winter one is not necessarily wrong.
What is abnormal is a step change with no change in schedule, or a bill that stays high after rain.
Finding an irrigation leak
Shut off the irrigation supply valve and watch the meter for an hour. If consumption stops, the leak is in the irrigation system rather than the house.
Then run each zone in daylight and walk it, looking for a head that will not retract, a soft wet area, or a zone that never fully pressurises.
- Isolate irrigation at its valve and read the meter
- Run every zone in daylight and walk it
- Look for permanently soft ground over a lateral
- Check the backflow assembly for weeping
- A valve that will not close fully runs continuously
The stuck valve
A solenoid valve that fails to close leaves a zone running continuously, sometimes at low flow that never shows above ground on clay.
The symptom is a wet area that never dries and a bill that does not respond to schedule changes. It is the most expensive common irrigation fault.
Reducing the bill legitimately
Correct the schedule for the season rather than running the same programme from April to October, and let fescue go dormant in high summer instead of fighting it.
Check whether the utility offers a separate irrigation meter, since sewer charges are often based on water use and irrigation water does not enter the sewer.