Posted in Product Information

Good things come in small packages

One of the key features of the Break Tank & Booster Sets we manufacture here at Arrow is their compactness.  All of the units are designed to be small enough to fit through a standard doorway, some are even designed to fit neatly inside a kitchen cupboard!  The benefits of having a compact unit are that installation is made easier and minimal room is taken up in the plant room, where free space is often at a premium.

Traditional Booster Sets tend to have large break tanks that store hundreds of litres of water – but are these really necessary?  The fear is if the tank is not large enough to store copious amounts of water, the pump will run dry and not be able to keep up with the demand.   The tank capacity on the majority of Arrow Valves units is only 24 litres – so are they not at risk of running dry?
The simple answer is ‘no’, but let us explain why…

The important difference between the small tanks on the Arrow Valves units and the much larger tanks on other units is the way they are filled.

The larger tanks are filled using a traditional Float Valve, similar to what you would see on a toilet cistern.  As the water level in the tank drops, so does the float, allowing water to flow in.  Once the tank is full, the float rises with the water level and shuts off the supply.  This is a simple and inexpensive way of filling, but does lack speed and accuracy.

The tanks on the Arrow Valves units are filled at a much faster rate using Solenoid Valves.  To give you an idea of how much faster, a DN20 Solenoid Valve is equivalent to ten ½” BS1212 High Pressure Float Valves.

Essentially, when you are using a Float Valve, the water is flowing into the tank at a much slower rate than it is exiting.  Therefore, you need a large body of stored water to prevent the tank from emptying completely.  In contrast, using correctly sized Solenoid Valves allows the water to enter and exit the tank at the same rate, preventing the need for excessive storage.

The role of the tank on our units is to act as a break (hence the name ‘Break Tank’!) between the mains supply and the boosted water, rather than acting as a storage tank.  The break (air gap) is a legal requirement for any pump greater than 12 litres per minute, and also prevents contamination for high risk applications.  Therefore, only the minimum amount of water needs to be held in the tank at one time – in fact, storing large amounts of water can become a potential health issue if it is not used regularly and becomes stagnant.

We have established that using a Solenoid Valve allows the tank size to be much smaller, but we also have to ensure that there is an adequate supply of water to the Solenoid Valve, to fill the tank at the required rate.  Each of the Break Tank & Booster Sets that Arrow Valves manufacture has a recommended supply pipe size, to guarantee the inlet flow matches the outlet flow of water.  As long as the correctly sized supply pipe is used, and you have a supply pressure greater than 1 bar (this is required to open the Solenoid) the tank should never run dry.

If you don’t have a large enough supply pipe or a supply pressure of at least 1 bar, then a small tank filled by a Solenoid Valve is not for you.  The tank simply wouldn’t have enough water coming in to fill sufficiently.  For this scenario, you would need a larger tank so that you have plenty of stored water ready to be used when needed.

To summarise…

Small Break Tanks won’t run out of water if they are filled at the same rate that they are supplying water.

Solenoid Valves can be used instead of traditional Float Valves to ensure tanks are rapidly filled.

If you have a small supply pipe or low pressure, you will need a larger tank to store water.

If you need any further information on this topic, or any other technical help, please feel free to give the Arrow Valves office a call or send us a message with any questions you may have.