When it comes to choosing a solenoid valve for tank drain it seems the options can be overwhelming. The first thing to look for is a zero differential solenoid valve. This means that it will work under zero head pressure so in theory you can drain your tank to the very bottom.
This is opposed to a differential solenoid valve that requires a minimum differential to operate (eg. a valve with a 0.3 Bar differential would stop working when your head pressure drops below 3m). The zero differential solenoid valves can either be direct acting (smaller sizes, say up to 3/8″) or coupled diaphragm (larger sizes, from 1/2″ to 2″).
A typical solenoid valve we use for zero or low head applications for water or non aggressive media is our ES55 series. This has all the features to look for when selecting the correct valve for this application. Another area where tank drain comes up regularly is for diesel farms. Using a zero differential valve here has the added benefit of being able to be used on the suction side of a pump. The valve to use here is our B55 series. This has a similar operation to the ES55 mentioned before but is designed for diesel and hydrocarbons (has viton seats and seals).
One thing to make sure in all applications is that the media is free from suspended solids that could get caught in the bleed whole in the diaphragm or wedged under the seat. This is especially true if it is a domestic rain water tank where leaves and other organic media can build up.
Check the video below related to B55 series Zero Differential Normally Closed Fuel Solenoid Valve:
Feel free to contact us to discuss your application further.