I plan to set up a small hydroponic system in my village allotment. I have some copper fittings left over from a kitchen renovation. I am concerned about using these because, although we have very little pilfering of produce from the allotments, the lure of stealing copper may be higher. Is there something cheaper and less attractive I can use instead?
Answer by RICK DONNAN
Quite apart from the risk of having copper or brass fittings stolen because of their high scrap value, they should never be used in hydroponics.
Because of the fertilisers in a hydroponic solution, it is very corrosive to metals such as copper, which is also the major component of brass. Therefore, your pipe and fittings would gradually corrode away until useless.
However, this is not the major reason for not using them. Copper is a plant trace element (also known as a micro-nutrient). In a hydroponic solution there is a range of copper concentration, which is essential for plant growth. Lower than this and the plant develops deficiency, which leads to reduced yield and quality. Higher than this and the plant develops toxicity (also known as phyto-toxicity), which leads to reduced yield and quality, and if it goes further, eventually to plant death. Using copper/brass pipes and fittings can easily lead to the copper concentration in the hydroponic solution rising to toxic levels, especially if the solution is recirculated.
Pipes and fittings for use in hydroponic systems need to be inert to corrosion. The usual material is black polyethylene (Polythene), which is relatively cheap and doesn’t corrode. It is readily available from hydroponic or irrigation retailers. Also, ensure that any pump you buy will also not corrode. Small pumps for hobby-sized systems are often plastic. Larger pumps often also have some components made of stainless steel. Ω
PH&G December 2015 / Issue 162