The DIY Part Fill Valve ensures that the water level in your tank is never lower than 7 cm. This means that you can use your rainwater tank to water your garden when you go on holidays. The rainwater tank will never run out of water.
There are other part fill valves available, but these require a plumber to install the valve inside your rainwater tank. The DIY Part Fill Valve is completely external to the tank and so it’s easy for anyone to install.
 
How to install the DIY Part Fill Valve,
Place the valve next to the tank so that the bottom of the valve is at the same level as the bottom of the tank. 
Connect the valve inlet to the mains water supply.
Connect the valve outlet (barbed) to the tank inlet.
Connect the barbed elbow to the tank outlet so that water can flow from the tank to the valve.
 If there is no vacuum breaker installed, connect a length of 13mm polypipe to the 13mm barb on top of the valve. The top of the polypipe should be higher than the tank inlet.
 
When the water level in the rainwater tank has fallen below 7 cm, mains water will start filling the tank until the water level reaches 10 cm. The water level cycles between 7 cm and 10 cm until it rains and the tank start filling with rainwater. Having purchased and installed the DIY Part Fill Valve, you are now ready to use the rainwater tank to automatically water your garden when you go on holidays.
 
It is recommendedthat you watch the Part Fill Valve video: