The underfloor heating manifold is a key component of an underfloor heating installation, but its correct connection - like that of most devices in plumbing - is crucial. Its task is to distribute warm water to individual heating loops and regulate the flow. This is exactly where the flow rates are set, the installation is vented, and the temperature in individual circuits is controlled. It is the heart and control point of the underfloor heating installation. Without correct manifold connection, the entire installation may operate unevenly or inefficiently.
The first issue is essentially the selection of the manifold, the decision whether it should be a brass model (more solid) or a slightly cheaper INOX manifold. The number of loops itself is, of course, determined by the design, that is how many heating sections we want to have. This is important, just like choosing a cabinet of the right size, but we assume that at this stage you already have that behind you, so we will focus on the actual connection of the underfloor heating manifold.
It starts, of course, with choosing the right location. If we do not have a design and it is not a new house where everything already has its designated place - the installation location of the underfloor heating manifold must be chosen appropriately. We are limited by the functionality of the rooms, but also by the possibility of connecting all loops. It is also important to always have unrestricted access to the manifold in case we want to check anything or, for example, vent the underfloor heating.
The underfloor heating manifold should be installed:
Most important rules:
The key thing: the supply to the underfloor heating manifold must be planned correctly.
The supply to the underfloor heating manifold consists of delivering the heating medium (water or glycol solution) from the heat source (e.g. a heat pump, boiler, or from a heat exchanger drawing heat from district heating, etc.).
A typical manifold connection layout:
the supply (hot water) goes to the rail with the flow meters - very important, it is recommended that the rail with the flow meters should be the inlet rail for the supply from the heat source.
the return (cooled water) goes back to the heat source - the rail without flow meters is recommended as the return rail
✅ Important:
the flow direction must match the markings (if the manifold is not double-sided and has such markings).
In the case of some manifolds, for example Nordic Tec brand, this does not matter and you can freely choose whether to connect the supply on the right or left side,
the supply and return must not be swapped
Basic mistakes to avoid - pay attention to the following:
✅ Size - the diameter of the pipe supplying the underfloor heating - which pipe?
The pipe selection depends on the system capacity and the length of the lines. The most commonly used are:
PEX / PERT / ALUPEX
diameters:
25 mm (the smallest and small installations)
26–32 mm (single-family houses)
larger for high flow rates
Rule:
A pipe that is too small will mean pressure drops and lower performance, as well as increased susceptibility of pumps to rapid wear, and possibly even certain failures over time. The standard for single-family houses from 80 to 300 m2 is 1 inch.
Once you know which side your supply is on and you have selected the location - we move on to the actual connection of the manifold to the underfloor heating, analyzing the more important elements step by step.
The underfloor heating sections - that is, the pipes - are connected to the manifold according to the obvious rule: the supply of the heating sections to the supply rail, and the return to the return rail. This is the absolute basis.
The outlets from the rails to the sections are usually 3/4", i.e. DN20. For this, we need 3/4" fittings reducing to the correct pipe size (this is a type of adapter). These should only be selected once we know what pipes we will use to supply the underfloor heating.
The most common standard in single-family houses is using 16 mm pipes with a 2 mm wall thickness, while 17 mm is used less often - basically only in larger buildings. Of course, there are other sizes as well.
We keep repeating it, but fittings must also be connected properly, ensuring tightness.
If everything appears to be connected, then we move on to the final steps and the test start-up of the system:
We emphasize that many manifold manufacturers state that the first commissioning of the installation should be carried out by an experienced professional.
Some of the mistakes are quite obvious, yet they still happen:
These mistakes can significantly reduce the efficiency of the system.
In many underfloor heating installations, a mixing group is used, which:
It is particularly important with:
In many cases, however, a mixing valve alone is enough, and in some systems even that is not especially necessary - for example, when the supply comes directly from a gas boiler or heat pump, where we can set a temperature suitable for underfloor heating right away.
Correct connection of an underfloor heating manifold requires:
If all these elements are carried out correctly, the installation will operate efficiently, evenly, and trouble-free for many years.
BLOG:
Low loss header in the central heating system - the most important information
Low loss header explained - structure, principles of operation, application
Choosing an underfloor heating manifold - what should you consider?
Compendium of knowledge about Underfloor Heating Manifolds - questions and answers
Types of underfloor heating manifolds and how they work
What pipes for underfloor heating - tips and tricks
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