Blumat pressure reducer

The Blumat pressure reducer sits between the tap and your supply hose and brings mains pressure down to 1 bar. It is the component that makes a mains-fed Blumat installation possible, and it is a requirement rather than an accessory.

Why a Blumat cannot take mains pressure

The regulating mechanism in a Tropf Blumat is a membrane that pinches a thin hose shut. That membrane is operated by the negative pressure building inside the ceramic cone as the soil dries, and that vacuum is small: it is the suction of moist earth, not a mechanical force.

Set mains pressure against it and you lose the balance the whole system rests on. The membrane can no longer hold the hose closed against the pressure on the other side, fittings start leaking, and sensors keep running even in moist soil. What you have then is not a demand-driven system but a leaking pipe.

The reducer brings pressure down to a level where the membrane can do its work. It therefore belongs right at the head of the installation, immediately after the tap: everything behind it runs on reduced pressure, everything before it on mains. If you plan to branch later, branch immediately after the reducer.

How much one reducer carries

This is the figure you choose it on: one reducer drives roughly 250 to 300 Blumat sensors, over distances up to about 50 metres. Below that, you need one. Grow past it and the answer is a second reducer, not more hose.

There is a height limit too

Less well known and easy to overlook: a reducer covers roughly one storey up and one down. On one level in a greenhouse this never arises. Feed a setup one floor above from a tap in a shed, or the reverse from a cellar, and you are at that limit.

The reason is the same as above: height difference is pressure. Every ten metres of height is about one bar, so a storey costs or adds a substantial fraction of what the reducer delivers.

Why a tap reaches further than a tank

A tank works on gravity, and that pressure depends on height. A reservoir hanging four metres above the sensors gives around 0.4 bar, where this reducer gives 1. You will not notice that in a small setup, but you will as soon as distance is involved: over tens of metres the mains route holds pressure where gravity fades away.

Against that, you are tied to the tap. To use rainwater or feed nutrients, a tank with a tank fitting is the route.

Before winter

Remove the reducer before frost and store it frost-free along with the sensors. The supply hose can stay outside; it is frost-proof. A reducer left full of water that freezes is a reducer you replace.

Technical Specifications:

• Output pressure: 1 bar
• Capacity: around 250 to 300 Blumat sensors
• Reach: up to about 50 metres
• Height difference: roughly one storey up and one down
• Connection: tap one side, Ø8 mm supply hose the other
• Position: at the head of the installation
• Winter: remove and store frost-free

Frequently asked questions

Can I connect to a tap without one? No. The membrane in the sensors regulates on very small pressure differences and will not hold mains.

Do I need one or two? One up to around 250 to 300 sensors and 50 metres. Beyond that, a second.

Can I feed a floor above? About one storey up or down is the practical limit.

Will it work on a pump? Yes, provided the pump delivers steady pressure.

Do I need it with a water tank? No, then you use a tank fitting and work on gravity.