This is an important factor to consider, as the quality of the water used will have an impact on the quality of the nutrient solution.

Even plain water will have nutrients and dissolved salts in solution, this means that the water used to make up the nutrient solution will give background levels of pH and conductivity.

Depending on the amount of hi-carbonates in it, water is described as being either hard (high levels of bicarbonates) or soft (low levels). The pH and conductivity levels of the different water types is given below.

It should be noted that these figures are approximate and some areas can have unusual readings due to elements added by the water companies. However, most of the U.K. falls into the range of ‘hard’ to ‘very hard’ water, with pH levels of around 7.00 — 8.5.

Both ‘very hard’ and ‘very soft’ water is poor quality water for growing plants. The addition of a ‘hard’ or ‘soft’ water type nutrient concentrate is recommended.

RAINWATER

Plants have developed over millions of years to feed from rainwater, so this is the best type of water to use when making up a nutrient solution. It is the purest form of water, with few or no dissolved salts, and therefore has low pH and conductivity levels. It can however be difficult to collect sufficient rainwater to maintain a hydroponic system.

If you can use rainwater, hold it in a covered tank, keep it clean and filter out any bits before use. Also, take care to ensure that the nutrient concentrate that you purchase is suitable for use with rainwater.

TAP WATER

The main problem with using tap water to make up your nutrient solution is that it contains high levels of un-dissolved salts, particularly sodium chloride. This is likely to cause a build up of salinity.

If using tap water it is best to leave it to settle for 24 hours. This will allow the water to adjust to room temperature and excess chlorine can evaporate off. Do not use hot water that has cooled down as this will contain no oxygen.