One station works sometimes, and not others

What has gone wrong

The station runs one day and not the next. You go out to look at it and it works, so you leave it, and a fortnight later it is off again.

Intermittent means a connection that is nearly making. A solenoid coil does not half-fail — it works or it is open circuit, and it stays that way. What comes and goes is a corroded joint in a valve box, making contact when the copper happens to be pressed together and losing it when the ground moves, the box dries out, or somebody walks over it.

This is the same underlying fault as several stations dying at once, caught earlier. A joint that is intermittent this season is a joint that fails completely next season.

Why this happens in Perth

Perth valve boxes go through a bigger wet-dry swing than most. They fill through winter, then bake dry from October, and a corroded joint behaves differently at each end of that cycle — wet corrosion conducts just enough, dry corrosion does not conduct at all. So the fault tracks the season rather than the schedule, which is exactly what makes it so hard to catch in the act.

The 1 June to 31 August ban compresses it further. The system comes back on 1 September after three months of doing nothing, into ground that is still damp, and the joint works. By November the box has dried out and it does not.

The underlying cause is nearly always the same: joints made with plastic screw connectors or twisted-and-taped, in a box that floods. That is not a Perth problem so much as a cheap-installation problem, but the sand and the flooding make it show up faster here.

Is this a DIY job?

Yes. Everything below is 24V AC or purely mechanical, which is the part of a reticulation system a homeowner can safely work on.

The wiggle test — five minutes, no cost, and it is definitive

You need the fault to be happening, or at least the station running.

1. Start the suspect station from the controller and leave it running.
2. Open the valve box for that station.
3. Take each joint on the two wires going to that solenoid — the station wire and the common — and flex it gently by hand. Not a yank; a bend, the sort of movement the ground gives it anyway.
4. If the station cuts out, or comes on, you have found it. That is the joint.

If nothing changes, do the same at the controller's low-voltage terminal strip: a wire that has worked loose in a terminal does the same thing. Only the wiring compartment — do not open the mains side.

Still nothing? Run the station and leave it running for a full cycle while you watch. Some joints only drop out once the ground has had water on it for ten minutes.

While the box is open, look at the other joints too. They were all made on the same day by the same person with the same connectors. If one is corroded, the rest are on their way, and redoing all of them now is one afternoon instead of four separate ones.

Fixing it

1. Turn the station off at the controller.
2. Cut the joint out. Do not try to clean it up and reuse it — corrosion wicks up inside the insulation further than you can see.
3. Strip back to bright copper on both sides. Bright, not dull. If it is still discoloured, cut back further.
4. Rejoin with a gel-filled waterproof connector. This is the whole repair, and it is why the joint you are replacing failed: whatever is in there now is not one.
5. Leave slack, and route the joint so it sits above the bottom of the box rather than in the puddle.
6. Run the station and do the wiggle test again on your own work.

Gel-filled connectors are sold as direct-burial or waterproof wire joiners, in packs. They are a couple of dollars each and they are the difference between fixing this once and fixing it every second summer.

What it costs

Finding it: nothing. The wiggle test is free and it is the whole diagnosis.

Fixing it: the price of a handful of gel-filled connectors. Buy a box rather than a pack of two — you will use them on every fault on this site.

If you pay somebody: unverified, and worth two quotes. Be aware this is a fault that is hard to demonstrate on demand — if it is working when they arrive, they are diagnosing from your description. Tell them you have done the wiggle test and what happened, and if you found the joint, say which one. That is the difference between a diagnostic callout and a ten-minute repair.

Common questions

Why does my sprinkler station work some days and not others?

A corroded joint that is nearly making contact. A solenoid coil does not half-fail — it works or it is open circuit — so anything intermittent is a connection, not a coil.

How do I find an intermittent reticulation fault?

Run the station, open the valve box, and gently flex each joint on the two wires by hand. If the station cuts out or comes on, that joint is the fault.

Why do reticulation wire joints keep failing?

Because they were made with plastic screw connectors or twisted and taped, in a box that floods. Only a gel-filled waterproof connector survives being underwater for years.