Watering Systems : Handy Hints and Installation Guide

Valve Construction and Operation

The Moss Control valve consists of a valve coil (the section with the wires attached), the main valve body (grey) and the threaded ring (black plastic or brass) which joins the two halves of the body. Inside the body is a flexible moulded diaphram seal and a small spring.

Water makes its way into the chamber on the top side of the internal diaphram causing it to press down and stop the water flow. This is its normal "off" position.

When electicity of 24 volts is applied to the valve coil, it retracts a small plunger which releases the water pressure on the diaphram seal, permitting full water flow through the valve body.

Moss Control Valves are very rugged but they operate in a harsh environment - hot summer sun, cold winter frosts, high water pressure, continual rain, and the occasional insect, animal or human to disturb the wiring.

It is not surprising then, that after a few years operation, some maintenance may be required.

Troubleshooting

Intermittent Failure

The most common sign of trouble is when the valve starts to intermittently fail to switch on.

Dry Joints

The usual cause of this is a "dry joint" in the wiring. Water or moisture gets into the exposed wire where it is joined and an oxide layer forms which decreases the electric signal. So undo all the joints, clean the bare ends of the wire with some "wet and dry" sand paper, and re-seal with insulation tape. This will usually fix the problem. Try to stop rain, or sprinklers reaching the joints and they will last longer.

Valve Coil

If the wiring joints have all been cleaned as above, and the problem persists, check the valve coil:-

Remove the wire from the coil and turn off the water to the valve. Unscrew the coil, anti-clockwise, and remove. Turn on the water to the valve. You should see two small streams of water come out of the control channels. This means they are clear and working properly. If water is not coming out of both, use a round wooden toothpick to unblock the holes.

While the coil is off the valve, check that it is working by connecting it to the transformer with a short length of wire. When the transformer is switched on, the small rubber plunger should snap in with a clicking sound. If not, the valve coil has failed and will need to be replaced.

Permanent Failure

Permanent failure of a valve component can be caused by a combination of high water pressure, high temperature from the sun, large pressure pulses due to "water hammer", expansion and contraction over a long time period and ultraviolet light.

Cracked Ring

If the large threaded ring which holds the valve together has cracked, it will need to be replaced. Early models had a grey plastic ring, later models had a black plastic ring and the current version uses a brass ring which seems to have eliminated this problem.

Cracked Valve Body

If there is a permanent leaking of water from the valve, first check all the threaded connections. If they are all secure, check for small hairline cracks in the body itself. If they exist, the valve will need to be replaced.

Split Diaphram

If the valve fails to turn off then most likely the diaphram inside has developed a split due to continual wear. Undo the large threaded ring which holds the two valve halves together (it is very tight and you need to hold it firmly). Be careful that you do not drop the small spring inside as you take the valve apart. Check the diaphram for splits. If so the diaphram needs to be replaced.

See also:

• Overview of Automatic Watering
• Small Control Valve
• Large Control Valve