Can I install a sprinkler system timer underground?

Question

I have a 4-zone sprinkler system. I had a construction crew at my house, and it appears they cut 1 of the 5 wires before pouring new concrete on top. Therefore, only 3 of the 4 sprinkler zones work.

Short of tearing out lots of concrete to find the cut wire, I cannot repair the wire. I tried letting 2 zones share one wire, but I don't have enough water pressure to support 2 zones at the same time.

The only thing I can think of is that I might be able to install the timer outside, underground in the box with the solenoid valves. I have a few questions...

Is this a feasible idea? If so, how should I do it?

• Are there any companies that make waterproof, underground timers specifically for this purpose? If not, can I use a "regular" timer that I put in a box?

• Where do I convert from 110V to low voltage? In the house or in the box? The four good wires are typical sprinkler wires (18 gauge?). Can this handle 110 AC electricity? Or should I use be using the "black box" to convert to low-voltage before using the sprinkler wire.

Timer | ------------------ 1 cut wire ---------------- | underground box in house | ================= 4 good wires =============== | with valves

Answer 1

You would not use the existing good sprinkler wires to bring the 120VAC out to the valve box. The wires are not rated and approved for that type of use. Place the converter transformer indoors to step the 120VAC down to the 24VAC. The "good" wires could then be used to route the 24VAC outdoors.

I would not use the sprinkler timer in the valve box. It would be very inconvenient to use it in that manner and the underground environment is highly likely to not be friendly to the control unit circuitry. Instead you should install an outdoor timer unit on an exterior wall above the valve box. (Use "outdoor sprinkler timer" in Google to see a selection of possible timers). The better outdoor timers have a lid that closes over the controls to protect the interior from the elements. You could then use a PVC conduit to route the necessary wires from the timer down into the valve box to keep things neat.

Do select the timer as one that works off the low voltage.

Answer 2

Keith, You can fish in a new wire under the cement. I have done this quite a few times using a 1/2" stick of PVC pipe connected to a water hose. Dig a small trench next to the cement slightly deeper if larger compacted rock was used some times it it is easier to go below the rock. Connect the PVC to a garden hose and start drilling your hole by pushing into the soil and pulling back. You will need a place for the water to drain to although sometimes after a few feet not much comes back. Just keep puling back and pushing forward. I have used this method to drill over 30' having 4 unions in the pipe (the unions make it a bit tougher).when I have the pipe to the other side dig down to it and ether use the pipe to pull the wire in or use the pipe like a conduit. I have used up to 1" pipe to do this 1" takes forever, 1/2" & 3/4" not so bad. I would pull in a extra line or two if 1 was damaged others may have had the insulation skinned and could fail at a later time. I think this would work better than trying to find a controller that is rated for an under water location (boxes in the ground during winter months regularly fill with water in most areas).