Calibrating a water-powered proportional dilutor

Water-powered dilutors can deliver not only fertiliser, but also treatments and essential additives to many parts of the crop. So it’s important to check their calibration regularly – at least once a year – to spot wear and tear or inaccurate dosing early.

This information was last updated in 2018.

The role of water-powered dilutors

A number of different types of dilutor, of varying levels of sophistication and available dilution ratios, are used on nurseries and farms.

When well-maintained, they simplify the application of accurate doses of soluble fertilisers, entomopathogenic nematodes and plant protection products to your crops. They can also be used to disinfectant hard surfaces or inject various acids and water treatment additives into stored water sources.

The information here about how to calibrate and maintain them should be used in conjunction with the AHDB video Calibrating a water-powered proportion dilutor.

How does it work?

A water-powered proportional dilutor injects a set amount of concentrate into the water passing through it so that it can mix with the water before it is pushed out of the unit and into the irrigation network.

The dose of the concentrate injected by the unit is proportional to the volume of water entering it. It is important to calibrate such units at least once a year to ensure they are still performing within the stated tolerance, wear and tear. Damage to key parts can impair their performance.

Calibration regime for a water-powered dilutor

Action points:

• Calibrate water-powered proportional dilutors every six months, or least once a year.
• Record the results and any action taken as a consequence, such as adjusting the dilution settings on the unit.
• Ensure any conductivity meter used in the calibration procedure is temperature compensated and calibrated.
• As part of the calibration process, take the opportunity to carry out other checks.
• Inspect the basket filter in the unit head (as appropriate) and the filter in the end of the concentrate extraction pipe to make sure they are clean and undamaged.
• Also check the ‘o’ ring washers on the valve seats in the unit head to ensure they are still in place.
• Do not leave any fertiliser solution in the dilutor over the winter period or during long periods of non-use.
• Wash the unit out with clean water before storing.

Calibration process

Calibrating your water-powered dilutor regularly is essential. It should be done at least once a year, and preferably every six months to verify that the correct levels of soluble fertilisers (and other substances) are being applied to crops through the unit.

Unit maintenance

Remembering a few key points about how your water-powered dilutor works will help you troubleshoot any problems and minimise the likelihood of damage or misfunction.

Acknowledgements

The guidance is based on the content of Bulrush Horticulture Grower Notes GN10. Thanks also go to Russell Woodcock and Gary Woodruffe, Bordon Hill Nurseries, for their time and input into the production of this information and the video dealing with the calibration of water-powered proportional dilutors.