Redesign, zone expansion and pressure correction

What is irrigation system redesign?

An irrigation redesign changes the hydraulic layout of a system you already own - splitting a zone that tries to run more heads than the supply can feed, adding zones for landscape that did not exist when the system was built, or regulating pressure that is outside the range the heads were designed for. It almost always reuses the existing mainline and much of the existing pipe, which is why it usually costs a fraction of a replacement.

Signs you need irrigation system redesign

• One zone consistently underperforms at its far end while the near heads look fine - the classic overloaded-zone signature
• Heads mist into fog rather than throwing droplets, in one zone or across the system
• You have added beds, a lawn extension, an island or a hedge that no head reaches
• Turf and planting beds share a valve, so one of them is always on the wrong schedule
• Rotors and fixed sprays are mixed on the same zone, which no schedule can reconcile
• A tree that was a sapling when the system went in now shades and blocks a whole arc
• You have removed lawn and the spray zone that served it is now watering gravel or hardscape
• An audit came back with poor uniformity that nozzle changes alone will not fix

Seeing something not on this list? Browse irrigation problems by symptom →

How irrigation system redesign actually works

1. 1

   Re-measure the supply - the number everything else depends on

   Static pressure and available flow are measured again rather than taken from the original design. Municipal pressure changes over decades, service lines corrode and lose capacity, and neighbourhood demand shifts.

   Watch forA redesign based on the original as-built figures. If the supply has degraded since installation and nobody re-measured, the new zoning inherits an assumption that is no longer true.

2. 2

   Map what is actually in the ground

   Valves are located, zones are traced, and head types and nozzles are inventoried per zone. On a system with years of repairs behind it, this stage routinely finds heads and nozzles that nobody intended to be there.

   Watch forSkipping the trace on the assumption that the as-built drawing is accurate. Repairs are rarely drawn, and a zone map that is a decade out of date makes every downstream calculation wrong.

3. 3

   Recalculate the flow budget and re-zone

   Total available flow is divided across zones so that no zone demands more than the supply can deliver at working pressure. Overloaded zones are split; zones whose planting has changed character are separated.

   Watch forA new zone simply teed off an existing one. This is the cheap version and it makes the original problem worse - the parent zone now has even more heads competing for the same flow.

4. 4

   Address pressure at the right level

   High pressure is corrected with pressure-regulating heads or stems, or with a regulator at the valve or at the point of connection. Low pressure at the far end is usually a flow problem, not a pressure one, and is solved by reducing what the zone has to feed.

   Watch forA booster pump proposed as the answer to misting. Boosting pressure that is already too high compounds the fault. Establish which of the two problems you have before anyone quotes hardware.

5. 5

   Match precipitation rates within every zone

   Every head on a zone should apply water at a comparable rate. That means one head family and matched-rate nozzles per zone, so the zone can be scheduled as a single unit rather than as a compromise.

   Watch forMixed brands left in place because they still work. A functioning head applying water at a different rate to its neighbours is a permanent uniformity fault, and it is invisible until you measure it.

6. 6

   Extend wiring and valve capacity for what you add

   New zones need a valve, a wire path back to the controller, and a free station on it. Where spares were pulled at installation this is straightforward; where they were not, the wire run is often the largest single cost of adding a zone.

   Watch forA controller already at its station limit. Discovering this after the trenching is done turns a zone addition into a controller replacement on the same invoice.

7. 7

   Convert bed zones to drip where it makes sense

   Redesign is the natural moment to move planted areas off spray and onto drip, because the zone is being reworked anyway. It removes the turf-versus-beds scheduling conflict permanently.

   Watch forDrip teed into a spray zone as a shortcut. Drip and spray apply water at rates that differ by an order of magnitude and must never share a valve, however convenient the pipe run looks.

8. 8

   Re-commission and re-programme everything

   After a redesign the whole system is re-run, arcs re-set, and the controller re-programmed - including the zones you did not change, since their share of the flow budget has moved.

   Watch forOnly the new zones being programmed. Re-zoning changes the hydraulics for existing zones too, and leaving their old run times in place undoes part of what you paid for.

What does irrigation system redesign cost?

Redesign is priced by the work involved rather than by property size: splitting a zone, adding a valve, running wire, and any new pipe. It reuses the existing mainline, so it typically lands well under a full replacement. See the Cost Guide.

See the full irrigation system redesign cost guide - by material, size and region →

If the number is the problem, here are the ways people pay for it →