Its all quite simple, we don’t have ‘training’ manuals, but underfloor is as simple as rads!

For the Heat Delivery side of the install:

Pipe lengths –
Pipes under the floor (with insulation below them) act as the radiator. 5m of pipe per sq meter of floor is usually suitable for a new well insulated house (up to twice as much in an old poorly insulated house).

Pipe runs of up to 100m long are best, over that the pressure and temperature fall off makes it harder to achieve consistency. Reduce the pipe runs to 75m in an older not so well insulated house.

The under floor pipes connect to a manifold, depending on how many runs of pipe you need will determine how many ports required on the manifold.

Checking for leaks or drops in pressure –
When you have your pipe laid, before you screed fill the pipes with water and leave it under pressure. If you connect to the manifold you can use that to check too.

Pex Pipe

The manifold with the flow gauges (the little clear plastic vials) is the return manifold, the other manifold is the flow manifold. Be sure you get all the air out of the system, it can take a bit of time to make sure it’s all out.

Boilers and controls –
The manifold connects to the boiler run (like a rad does). If the boiler has a high temperature output like a gas or oil boiler you will need some form of thermostatic control to reduce the temperature of the water circulating in the floor. This is usually a thermostatic blender valve. If you need a pump too you can make this easier still with a thermostatic and pump blender kit which bolts straight onto the manifold.

2 Port Manifold Cropped SML

For the control side:

Existing radiator run –
If you’re connecting your underfloor to an existing radiator run you might find you can just use your existing controls. The underfloor would come on and off with the radiators.

Thermostat + Motorised valve –
You can use a thermostat and a motorized valve in the run from boiler if all the underfloor zones are going to be on at one time.

Zone / Pipe run control –
For more control over each zone or pipe run you can use actuators on the manifold (they screw straight on). The manifolds port actuators (singly or in multiples) can be controlled by a thermostat. You can have a separate room thermostat control on each port / zone if you require complete control.


You will need to connect the actuators (at the manifold) to the Thermostats (in the rooms). You can use wired or wireless control. Wired is more economical and robust. You need cables e.g. 1.5m 3
core flex) running from the manifolds to thermostats, usually both are wired to a Wiring Centre Controller which can be put where ever it’s convenient (it’s usually near the manifold).

Underfloor Heating Actuator (2)

Adjustment –
Just like radiators can be adjusted, the flow through each port of underfloor pipe can be adjusted at the manifold to balance the system. The flow gauges give an indication of the rate of flow through each port. Adjust these up and down by pulling up the lock ring (red) and turning the flow meter clockwise (reduce flow) or anti clock wise (increase flow). When adjusting remember that underfloor changes temperature more slowly than radiators and you should make small adjustments each time.

The thermostatic mixer also blends the flow with the return to moderate the heat in the pipes and is adjustable to increase or decrease output too.

Conclusion –
We hope this guide was useful! If you have any other queries please do not hesitate to contact us on (01636 639900) or email

We sell most things you need from underfloor to heat pumps and solar so please ask if you need anything!