This unvented cylinder upgrade was a project we carried out for a repeat client of ours. While working on another project at the property, the owner told us that they were about to replace their bathroom. This was to be supplied and installed by a different company – but the owner had major concerns about the lack of water pressure.

Because the building in question is an old farm house converted into two properties, the side of one of the properties was left with a Primatic Hot Water Cylinder.

With a Primatic Hot Water Cylinder, the water for the central heating is separated from the domestic hot water by an air lock inside the heat exchanger. The Primatic Cylinder is supplied from a cold water storage tank, which also feeds the central heating system. There is no need for a separate header tank for your heating. The central heating flow and return pipes are connected to the cylinder.

Only an air gap separates the central heating water from the domestic hot water. When this air gap is charged, the system will work perfectly. Your hot water will be heated as it would with a conventional system.

However, when the air gap is lost, the two systems will mix. This leads to slight discoloration of the water coming from your hot water tap.

With this type of system, the client faced two main issues.

Firstly, they couldn’t increase the hot water pressure using a shower pump which, under normal circumstances is a feasible option. But with a Primatic system, the water supplies would mix.

Secondly, they had been experiencing issues with circulation on the central heating side of the system. Radiators were not getting hot or taking too much time to warm the house. Normally, we would flush the heating system with suitable cleaning products. But with a Primatic system you cannot do that. Adding chemicals to the cold water storage tank would also mean adding chemicals to the hot water. Not a good idea.

After considering the options, we decided that the best idea would be to upgrade the hot water system with an unvented cylinder. This gave them the opportunity to relocate the system and free-up space for a walk-in shower.

An unvented cylinder is a sealed system. Hence, the hot water storage did not need to be reconnected. However, because the airing cupboard was now being used for the walk-in shower there was no room for a new header tank to supply the heating. A better and more convenient option was to seal the heating system with an expansion vessel.

An obvious advantage of an unvented cylinder is pressurised hot water. Another is the ability to balance the cold water system with the hot. This is becase an unvented cylinder reduces the pressure within the cylinder to a maximum of 3.0 bar.

If the cold incoming main is higher than this, running it to a mixer tap or shower outlet can cause poor flow or temperature control. By supplying cold water to these ‘mixed’ outlets from the balanced cold water side of the cylinder, you can ensure issues don’t arise from unequal pressures.

We installed full flow, colour coded lever valves to each pipe of the domestic water system to allow the client to isolate as required.

Better still, a new pump and motorised valves were also added, giving the client complete control of the heating and hot water independently.

Furthermore, the introduction of a Nest Learning Thermostat added to the improved level of heating management.