Cheap float valve saves valuable resource


By Charl Van Rooyen | 20 September 2017
float valve
When the reservoir is full, the float valve shuts off the water supply from the windmill so that it will not overflow. PHOTOS: Supplied

The addition of a float valve to the pipe supplying water to the reservoir has helped this cattle farmer to prevent his reservoir from overflowing and wasting water – without the windmill’s brakes needing to be applied.

float valve
Mr. Abri Steyn and his girfriend, me. Jolanda van Wyk.

Thanks to a float valve at the end of the pipe supplying water to the reservoir, it is no longer necessary for the windmill’s brakes to be applied to prevent the reservoir from overflowing. With this small adjustment that only cost around US$45 (K430; R600), Abri Steyn, a cattle farmer from the farm Leeufontein near Wolmaransstad in the North West province of South Africa, saves a lot of water that would otherwise be wasted.

float valve
The plastic pipe must go through the foot plate right to the bottom of the borehole otherwise the borehole can become silted up in sandy regions.

He uses windmills to supply drinking water to his cattle. He says that a windmill is a reliable machine and, for many farmers, critical for the pumping of fresh water to a reservoir or water tank.

A reservoir regularly overflows if there is a strong wind. This overflow isn’t utilized and the water puddles around the reservoir, creating muddy conditions.

float valve
If the reservoir continually overflows, the ground around it will eventually look like this from all the water.

He decided there had to be a way to prevent this wastage of overflowing water without having to apply the windmill’s brakes.

The solution occurred to him while he was fitting a new float valve to a water trough. “When the trough is full, the float valve closes and the trough doesn’t overflow. If the same principle was applied to the reservoir, then it too wouldn’t overflow,” he says.

He then fitted a float valve to the end of the pipe that supplies water to the reservoir. Once it is full, the float valve closes and the water from the windmill no longer flows into the reservoir. Normally this would cause the water to push up and run out at the top of the borehole pipe.

float valve
The water would normally push up and run out at the top of the borehole pipe but now the float valve closes and prevents the water from flowing into the reservoir.

To prevent this, Steyn loosened and removed the pipe, cut a hole in the pipe and welded a slightly curved connector to the borehole pipe. He then carefully rinsed out the pipe to remove any loose bits of metal that might be in it, otherwise they could drop down to the cylinder at the bottom of the borehole and damage it.

A piece of plastic pipe with a 25mm diameter was then fitted to the connector so that the water that was pumped to the top by the windmill could run back down the borehole when the float valve is closed. It has to be long enough to reach right to the bottom of the borehole. In this way, all the water that would have overflowed from the reservoir is returned to the borehole and nothing is wasted.

float valve
The connector that allows the water to run back into the borehole. It is easy to fit this pipe.

Abri sums up the benefits:

• The system automatically controls the reservoir’s water level.
• It is cheap and easy to implement and saves a lot of water.
• The foundations of the reservoir remain dry because there isn’t water running over the edge. Reservoirs or cement dams are inclined to crack if the foundation is on wet ground.
• The windmill’s brake no longer has to be applied.
• If the farmer doesn’t want the surplus water to be returned to the borehole, it can be redirected for other purposes such as filling water tanks or irrigating plants, vegetables or lawns.

There are, however, a couple of disadvantages:

• The water being returned to the borehole can cause loose soil and bits of rust to be washed down. A borehole in a sandy region could become silted up. It is therefore important for the plastic pipe to be lowered to the very bottom of the borehole.
• The connector must be above the maximum water level of the reservoir. If it is welded at the incorrect height, the water will not be pumped into the dam while the float valve is open.

Abri says it cost him only R600 to make this adjustment to the windmill, which is negligible when compared to the water saved.

Enquiries: Abri Steyn, email: abrie.steyn@gmail.com.