Water Boosting

Unvented water systems require good pressure and flow from the incoming mains supply. Even if it’s good, is it sufficient for the combined usage requirements? For example, properties with shared mains, multiple bathrooms or multiple high demand outlets.

Symptoms may be reduced performance when using multiple outlets. Such as, running a tap or shower, using a washing machine or flushing a toilet. If other outlets are affected, it may be insufficient pressure and/or flow. Poor system design, incorrect pipe sizing or general cost cutting may also be a contributing factor!

In this situation, an Accumulator or Pump Set may provide the ideal solution. It also offers other benefits! Both accumulators and pump sets serve the same purpose, but there are notable differences between the two. These are explained below.


Accumulators store water at mains pressure. They connect directly to the incoming mains supply, providing a buffer store of pressurised water. Similar to a rubber balloon filled with water!

When the system is designed and installed correctly, multiple outlets can be serviced at high pressure, with no drop in performance. These are well suited to properties with multiple bathrooms with simultaneous usage.

Accumulators store water up to the static pressure of the incoming water mains. If the incoming mains pressure is low, say 1.0 bar, then a charging pump may be required to ‘top-up’ the pressure. Most unvented systems operate at around 3 bar pressure. For anything below this, a charging pump will help optimise performance.

Accumulators are very efficient and reliable. They simply use energy from the water supply to fill and pressurise a sealed hygienic container. This is stored under pressure as wholesome drinking water, until required. Accumulators are maintenance free, silent and and can be located more-or-less anywhere in the property.

Accumulator systems are modular. Several may be specified or additional ones may be added at a later date, if necessary. Accumulators are generally the preferred choice where there is good static pressure, but poor flow rates.

Boost a Main

The video below demonstrates the benefit of an accumulator with a charging pump. The results are extremely impressive!
It shows a single shower, and then a second, third and forth are switched on. With four simultaenous outlets, the flow reduces to a barely a dribble. Switch on the accumulator, and you instantly have full flow to all four showers. When designed and sized correctly, accumulators can service as many outlets as required!

Pump Sets

Pump Sets consist of  a booster pump(s), a cold water tank, a small accumulator vessel, and some controls. They are ideal for situations where accumulators are not viable. Maybe due to higher pressure requirements or imnsufficient pressure. Due to pump noise, these would generally be sited away from sleeping or quiet areas.

Typically, two pumps are used to provided duty/assist operation, with both pumps only running together at maximum load. Additionally, the use of two pumps provides a level of redundancy should one pump fail. This is very important. The cold water tank must be sized to provide both hot and cold supplies at maximum usage.

Whereas accumulators make use of energy from the incoming mains, Pump Sets rely solely on the pumps to provide the pressure and flow to service the outlets and unvented cylinder. This may be the preferred option for larger properties that require higher pressures with a high usage demand.

Pump sets would be the preference for larger properties with multiple high performance bathrooms.

An added benefit of having accumulator(s) or a pump set is the availability of stored water in the event that the mains water supply is interrupted.

Please contact Apex Plumbing and Heating to discuss your requirements or to arrange a free on-site survey.

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