Most of the pressure gauges used on espresso machines are made by one Italian company, which is called Orman Manometri. They produce a variety of pressure gauges.
There are basically 2 types of pressure gauge. A single and a double pressure gauge. The single pressure gauge can be a pump or a boiler pressure gauge. The pressure gauge has a pressure range normally of 0 up to 16 bar. The boiler pressure gauge normally has a pressure range going from 0 up to 2,5 or 3 bar. This does depend on the requirements of the manufacturer.
The other type is the double version. With this type of manometer you have a pump and boiler pressure gauge in one. This means that you have 2 individual fittings on the back. In most cases the pressure gauges have a male 1/8” BSP-G thread. In some cases this is a conical fitting.
If you have a OEM/original or a after market pressure gauge, they are technically the same. The difference is that a after market pressure gauge can be aesthetically slightly different and that the brand name is printed on the face plate.
The boiler manometer gives a idea how much pressure inside the steam boiler is. You see the pressure rising from 0 up to a set pressure with the pressure switch, when you want to adjust the pressure switch you use this pressure gauge to see on which pressure it will switch off.
When your boiler doesn’t have a vacuum valve, which was common in the past. The initial reading can be incorrect. Seen the pressure switch does switch off, but the reason for this is that there is false air. So you have the idea that your boiler is up to temperature. But in reality your boiler isn’t. This can be resolved by turning the steam valve knob open and closed. Then you see the pressure dropping rapidly.
The pump manometer is only readable when the pump is running. When the pump is running you can use the adjustment screw on the side of the espresso machine pump. By turning the screw inwards the pump pressure will increase, when you turn it outwards the pump pressure will decrease.
In almost every case the pump pressure is not measured at the brewing group, so the pressure shown on the pressure gauge is not the brewing group pressure.
