Which underfloor heating manifold do I need? Counting loops, with or without a pump, composite or steel, and connecting to a boiler or heat pump

Short answer: count one loop per 12 to 15 m² of floor (maximum 100 to 120 metres of pipe per loop with 16 mm pipe), and add one extra loop as a reserve. If the manifold is connected to a boiler that also feeds radiators, you need a manifold with a pump and mixing valve that mixes the 70 °C water back down to 35 to 45 °C. If it is connected to a heat pump or a boiler that only heats the floor, a manifold without a pump is sufficient. Composite is corrosion-free and lighter, steel is the traditional alternative. In our shop a composite manifold with an A-rated pump costs € 730 (2 loops) to € 1,410 (9 loops), and without a pump from € 640 for 5 loops.

Step 1: the number of loops

A loop is one circuit of pipe from the manifold through the floor and back. The longer the loop, the greater the resistance and the colder the end of the loop. That is why, with 16 mm pipe, a maximum of about 100 to 120 metres per loop applies. At 10 cm pipe spacing there are 10 metres of pipe per m², at 15 cm about 6.7 metres. That gives the rule of thumb: 10 to 12 m² per loop at 10 cm, 15 to 18 m² at 15 cm. Each room gets its own loops, so you can control or shut off each room separately.

Situation	Floor area	Loops	Suitable manifold
Bathroom or one room	up to 25 m²	2	Robot LTVC 2-loop with pump € 730
Living room and kitchen, flat	35 to 50 m²	3 to 4	3-loop € 815, 4-loop €900
Ground floor, mid-terrace house	50 to 70 m²	5 to 6	5-loop € 1,069.50, 6-loop € 1,155
Ground floor, end-of-terrace or semi-detached house	70 to 100 m²	7 to 8	7-loop € 1,240, 8-loop € 1,325
Entire floor, detached house	100 to 130 m²	9 or two manifolds	9-loop € 1,410

If in doubt, choose a manifold with one loop more: a closed-off loop costs nothing, one loop too few means 140-metre loops that never get properly warm.

Step 2: with or without a pump and mixing valve

Underfloor heating works at a flow temperature of 30 to 45 °C. A boiler that also feeds radiators delivers 60 to 80 °C. Something has to sit in between: a mixing valve (thermostatic valve on the manifold) that mixes in return water up to the set temperature, and a dedicated pump that pushes the mixed water through the loops. This is called a low-temperature manifold or control unit, and it is essential as soon as the boiler supplies water hotter than the floor can take. An unprotected floor at 70 °C leads to cracks in the screed and sore feet.

You can do without a pump and mixing valve if the heat source itself already supplies low temperatures and has enough pump capacity: a heat pump, or a boiler that feeds only underfloor heating and is set to 45 °C. Then you choose a direct manifold, such as the Robot LTC 5-loop (€ 640.13). With a heat pump, a mixing valve is actually undesirable: it lowers the return temperature, and that costs efficiency.

Heat source	Flow	Manifold
Boiler with radiators and underfloor heating	60 to 80 °C	With pump and mixing valve (LTVC)
Boiler, underfloor heating only	40 to 45 °C set	Without a pump possible if the boiler pump can handle the resistance; with a pump for more than 5 loops
Hybrid heat pump with boiler	Variable	With pump and mixing valve, set to the floor temperature
All-electric heat pump	30 to 45 °C	Without a mixing valve; a pump only if the heat pump does not have one itself

An A-rated pump, such as on the Robot LTVC series, uses 5 to 20 W instead of the 60 to 90 W of an old pump; over a heating season that easily saves 30 euros in electricity.

Step 3: composite or steel

Steel manifolds were the standard for years and are still available, such as the Robot Standaard PRO 5-loop (€ 926.63) and the Stads PRO 5-loop (€ 1,122). Steel can rust if oxygen gets into the water, for example via pipe without an oxygen barrier or through frequent topping up. Composite manifolds are made of plastic with brass connections, do not rust, weigh less and have become cheaper in recent years. For a new installation with 5-layer pipe, composite is the logical choice; choose steel if you are replacing an existing steel manifold like for like or have a very high water pressure.

What else you need

• Pipe: 5-layer PE-RT or PEX with an aluminium or EVOH oxygen barrier, 16 × 2 mm; a 400-metre roll costs € 847.50, 600 metres € 1.270,50. Reken 8 tot 10 meter per m².
• Couplings: pipe adapters per loop (two per loop) and a repair coupling as a spare.
• Control per room: a MT-4 thermal actuator (€ 21.95) on each loop and a DT4M thermostat (€ 72.95) or wireless Robot thermostat per room, controlled by a Honeywell HCC100 controller (€ 298.95) for up to 10 zones. Without room control all loops are always open and you only control via the room thermostat.
• Automatic air vent and fill/drain valve: fitted as standard on the Robot manifolds; order separately for a bare manifold.

Connection and balancing

The manifold is mounted in an accessible place, as centrally as possible above the floor loops, with the flow at the top and the return at the bottom. Connecting it to the central heating system on the water side and filling and flushing the loops is work for an installer or an experienced DIYer; balancing the flow meters per loop determines whether every room gets equally warm. If a loop does not get warm after installation, read Underfloor heating not warming up. The complete approach, from installation to costs, is in Installing underfloor heating 2026. All manifolds and accessories can be found in the underfloor heating category; Instalpunt does not install, so have a qualified local installer lay the system. For questions, use the installation service.

Frequently asked questions

Can I buy a 5-loop manifold and use only 3?

Yes. Close the unused loops with the handwheels or a blanking cap. That is the usual way to keep spare capacity for a later extension.

What should the mixing valve be set to?

For a sand-cement screed 35 to 45 °C; for wooden or laminate floors a maximum surface temperature of 40 °C and therefore a flow temperature of around 35 °C. The exact value depends on the insulation and floor build-up.

How many loops can the boiler pump handle without a separate pump?

Usually three to four short loops. Beyond that the resistance becomes too high and the last loops get too little water. In that case, choose a manifold with its own pump.

Is the manifold also suitable for electric underfloor heating?

No. Electric underfloor heating works with heating mats and a thermostat, without water; see the Robot heating mat 4 m² with Wi-Fi thermostat.