# How to add a controlled amount of a nutrient solution to a water line

I have an existing water supply system for the cattle on my farm whereby 6 troughs located in different fields are all fed from a common header line. The pressure in that line ranges from 3-5 bar (It’s well water supplied from a submersible pump). Water is supplied to each trough based on the water levels using a mechanical ball-cock system. Currently I need to visit each of those 6 troughs each day to manually add a liquid mineral solution (to provide extra nutrients to the cattle at this time of year). That solution comes in the form of plastic drum. Currently I distribute about 350ml of that solution in total daily which covers 60 cows

I would like to automate this process in some way so that I can feed the solution directly into the header line. What would be the best way of doing this to control the supply of the nutrient solution? I only want to add the solution when there is flow in the header line.

• How exact does the dosing have to be? How long is the longest water pipe to a through, how long the shortest from a common accessible point? Can you provide a sketch of the layout? How much water do the 60 cows drink each day, same for summer and winter?
– mart
Jan 10, 2020 at 12:27
• If I understand correctly, you need to meter a specified amount once per day to each of six troughs via the resupply pipes. I assume the troughs refill at least once per day. What is the flow rate and daily demand on each of the six pipes? We need a sense of the cycle rate and duration. Jan 11, 2020 at 1:51
• My first thought is to supply each daily dose to a small mixing tank beside each line, then induce a small percentage of flow through the tank when the pipe is flowing. This separates the dosing from the random refill on the tanks. And it allows simple monitoring via counters and such. Jan 11, 2020 at 1:57

Our water purification system uses an injection pump, in this case a diaphragm style pump. It has a control for volume dispensed during operation. The operation is limited to when water is flowing by a water flow switch. When water is moving through the system, a small hat is lifted and closes a reed switch, activating a relay in the controller, which then operates the pump.

I'm confident that one can create a similar design using off-the-shelf components, as this particular unit, configured by a local plumbing supply house, was overpriced. Water flow switches are not uncommon now, but when I made the purchase, I was mostly ignorant of such things.

From Amazon, as an example: water flow switch

Then a type of pump that can do precisely controlled delivery is called a peristaltic pump.

It is basically a tube compressed by rollers and as the rollers roll over the tube a precise amount gets delivered.

You will have to check the max working pressure.

• I'm familiar with those pumps. How would you control it so that it only operates when the water line is flowing? Jan 10, 2020 at 13:07
• Use a flow switch - many types available. Jan 10, 2020 at 14:11
• @Sperick not easily if you want a controlled dose. Just dispense each dose daily (or twice per day, etc) to a tank, and bleed some pipe flow through the tank. Jan 11, 2020 at 2:13