Installation of a stainless steel floor heating distributor – step by step

We are still preparing products.

But you can look at other categories.

Installation of a stainless steel manifold for floor heating – step by step

Floor heating is now standard in new buildings and renovated homes. The heart of the entire system is the manifold – it manages the water flow to individual circuits, allows their regulation and balancing. A stainless steel manifold represents a reliable and long-term solution, but its correct installation requires precision, systematic approach and knowledge of several technical principles. In this article, we will go through the entire installation from the first planning stage all the way to system start-up – including common mistakes from practice that it is worth paying attention to.

If you are still in the product selection phase, we recommend first reading the article How to choose a stainless steel manifold for floor heating – number of circuits, diameter and flow, or How many circuits does the manifold need – how to correctly determine the number of floor heating circuits. These topics are a prerequisite for what we describe here.

What you will need before starting the installation

Good preparation is the foundation. From my own experience, I know that most problems during installation arise not from lack of knowledge of the procedure, but from insufficient preparation of the work area or missing tools at a critical moment. Before starting the work, prepare the following:

Manifold of the correct size – e.g. stainless steel 4-way manifold for floor heating for a typical family home with three to four rooms
Manifold cabinet or brackets for mounting – see also the article Mounting and installation of the manifold cabinet – where and how to install the manifold
Flange wrenches (fixed and extensions), torque wrench, screwdriver
Hose clamps, PEX or PE-RT pipes for individual circuits
Compression fittings or press-fit fittings according to the type of pipe system used
Teflon (PTFE tape) and/or seals – depends on the type of thread
Drain valve (manual or automatic) – most stainless steel manifolds have it included in the set, but check
Drain cock on the bottom of the return manifold
Pressure gauge for pressure testing
Water level and pencil for marking the cabinet position
Drill with hammer function, appropriate drill bits (for brick, concrete or drywall)

Important: the entire set of accessories should be prepared before you start connecting the pipes. Interrupted work – when you go to look for a certain fitting – can cause the seal to dry out or the pipe to shift.

Phase 1 – Planning the manifold location and circuit routes

The manifold must be placed so that the distances of the individual circuits to it are as uniform as possible. In practice, this means placing it mostly in the center of the layout – hallway, technical room, or closet. If you have a two-story building, typically one manifold per floor.

The height of the cabinet-mounted manifold is usually standard so that the bottom edge of the cabinet is 150–300 mm above the finished floor (or above the raw floor, if we are considering a layer of floor heating and a final surface). A manifold placed too low complicates the feeding of the circuits and prevents full manipulation when adjusting the flows.

The routes of the circuits should be laid in the floor so that they do not unnecessarily cross and each loop can be safely stretched without sharp bends. The minimum bending radius of a PEX pipe Ø16 mm is usually 8× the outer diameter, i.e. at least 128 mm. A smaller radius risks wrinkling or permanent deformation of the pipe, which reduces flow and lifespan.

Phase 2 – Mounting the manifold cabinet and securing the manifold

If you are using a wall-mounted manifold cabinet (recessed or surface-mounted), first mount it to the wall or fasten it to the wall – according to the chosen design. Check the level for horizontal and vertical alignment. The cabinet must be firmly secured – subsequent pulling of hoses and the force when tightening fittings must not cause movement of the cabinet.

Then you mount the manifold itself into the cabinet (or onto the brackets). The manifold consists of two bars (manifolds) – the supply (flow) and return. These bars are connected by side threaded extensions (outlets), to which the individual floor heating circuits are connected. Between them are usually also valves, flow meters and thermostatic heads.

During installation, make sure that the supply manifold is always on top and the return manifold at the bottom – this is the standard and ensures correct circulation and easier air venting. Most manufacturers color-code this (red = supply, blue = return).

Phase 3 – Connecting the supply and return piping from the heat source

The manifold is fed from the boiler (or from another source – heat pump, solar) via the main supply and return piping. These are usually made of copper or PP/PE material, with a diameter ranging from 22 mm to 28 mm depending on the system's power.

The manifold has external or internal threads at its ends – typically G¾" or G1". When connecting, always use sealing – either thread sealing (hemp fiber with paste or PTFE tape) or flat rubber sealing washer, depending on the type of thread on the given part. Never mix both methods at the same time.

Important: before connecting the manifold to the boiler piping, always close the main shut-off valve and isolate the pressure in the system. Always work on dry surfaces.

Phase 4 – Connecting individual floor heating circuits

This is the most extensive and important part of the installation. Each floor heating circuit consists of one pipe loop (usually PEX-A, PEX-B or PE-RT with a diameter of 16 mm or 17 mm), which runs from the supply manifold outlet, covers the entire heated room area, and returns to the return manifold outlet.

Connecting one circuit step-by-step:

Cut the pipe with pipe cutters at a right angle – a beveled cut will cause a leak
Put on the compression ring and nut (if you are using compression fittings EK or similar)
Insert the insert into the end of the pipe so that it fits snugly
Put the nut on the manifold outlet thread and tighten by hand, then with a wrench by ¾ of a turn
Do not over-tighten – stainless steel has softer threads than brass and excessive force can damage the thread

If you are working with a press-fit system (crimping), the procedure is different – insert the pipe into the fitting and use crimping pliers to compress the ring. This connection is then permanent and cannot be disassembled without damaging the fitting.

From practice: a very common mistake is mixing up the supply and return outlets when connecting multiple circuits. Get into the habit of immediately labeling each circuit with colored tape or a label – for example, "C1-living room", "C2-bedroom". It will save you hours of balancing during hydraulic balancing.

For a larger family house with five or more rooms, we recommend looking at the stainless steel 6-way manifold for floor heating, which can cover up to six separate circuits with full individual control of each.

Phase 5 – Pressure test before floor pouring

This is a step that must never be skipped under any circumstances. Before pouring the pipes into cement screed or anhydrite, you must pressure test the entire system. If a leak appears later under the poured floor, the repair is extremely costly and complicated.

Pressure test procedure:

Close all circuits except the one being tested (or test the entire system at once)
Fill the system with water, making sure to bleed air (open the air vents on the manifold)
Use a hand pump (or electric pump) to increase the pressure to 1.5× the operating pressure – typically 6 bar for systems operating at 4 bar
Let the pressure stabilize for 30 minutes – it may slightly drop initially due to the elasticity of the PEX pipe
Monitor the pressure gauge for the next 24 hours – the drop must not exceed 0.2 bar
Visually inspect each connection on the manifold and each pipe passage through the wall

If the pressure drops significantly, systematically search for the leak – the easiest way is to apply soapy water with a brush to each connection. Bubbles will reveal the location. Never pour the floor until the pressure test is successfully completed and documented.

Phase 6 – Setting up flow meters and hydraulic balancing

After a successful pressure test, one of the most important phases of the entire process follows – hydraulic balancing. Without it, the system will operate unevenly: shorter circuits will overheat adjacent rooms, while longer ones will "starve". The result – some rooms will be overheated and others cold, despite the boiler working at full capacity.

Stainless steel distributors are equipped with flow meters on the supply manifold. The flow meter indicates the actual flow in the respective circuit in l/min and also allows manual throttling (closing) of the outlet.

Basic balancing procedure:

Start the circulation pump and let the system run for at least 30 minutes at full flow
Read the flow on each flow meter indicator
Compare the actual flow with the calculated one (based on the circuit's power and temperature drop)
Throttle shorter/more powerful circuits by rotating the flow meter adjustment ring
Leave longer circuits fully open or slightly throttle them just enough to balance the total system flow
After each change, let the system stabilize for 20 minutes and read the values again

A more detailed procedure including calculations can be found in the article Hydraulic balancing of circuits via a stainless steel distributor – why and how to do it. This is a topic that deserves its own article, as incorrect balancing is the most common reason for customer dissatisfaction with underfloor heating, even in properly installed systems.

Phase 7 – Installation of thermostatic actuators and connection to the control unit

If you plan zonal control – and we recommend it for everyone – install a thermostatic actuator on each circuit (or group of circuits in one room). It is mounted on the thermostatic valve in the return manifold. The actuator is electrically operated (24 V or 230 V) and opens or closes the respective circuit when receiving a signal from the room thermostat.

The actuators are connected by cable to the control unit (controller), which collects signals from all room thermostats and coordinates the opening and closing of circuits, as well as the switching of the boiler and pump. This wiring must be carried out professionally – for 230 V actuators, exclusively by an electrician.

Practical tip: route the cables from the actuators so that they are clear – label each one the same as the corresponding circuit. Place the cabling in a plastic conduit or cable tray inside the distributor cabinet. This will save you an hour of searching a year from now when you need to replace a thermostat or actuator.

Phase 8 – Air venting and first system start-up

Before full start-up, it is necessary to purge the system of air. Air in the pipes causes noise, reduces flow and can damage the circulation pump. Procedure:

Close all circuits except the first one
Open the air vent on the top manifold
Let the water flow until a continuous stream without bubbles appears
Close the vent and open the next circuit – repeat the procedure
Finally, purge the entire system at once with the pump running
Check the system pressure – fill water to 1.5–2 bar operating pressure

More about air venting, including work with automatic air vents, can be found in the article Maintenance and air venting of a stainless steel underfloor heating distributor.

Typical dimensions and technical parameters of stainless steel distributors from Hepworth

For proper installation, it is important to know the basic dimensions and parameters of the products you are working with. Detailed dimensions can be found in the article Dimensions and pipe thread spacing of stainless steel distributors from Hepworth. Here we provide approximate values for everyday use:

Distributor	Number of outlets	Outlet spacing	Supply/return thread	Max. pressure	Max. temperature
2-way	2	50 mm	G¾" / G1"	10 bar	110 °C
3-way	3	50 mm	G¾" / G1"	10 bar	110 °C
4-way	4	50 mm	G¾" / G1"	10 bar	110 °C
5-way	5	50 mm	G¾" / G1"	10 bar	110 °C
6-way	6	50 mm	G¾" / G1"	10 bar	110 °C

Note: Always check the exact dimensions in the technical documentation for the specific product, as the manufacturer may update them. A 50 mm spacing between connections is important when planning the space in the cabinet – a 6-way distributor alone will take up at least 350 mm in width.

Most common installation errors from practice

After years of experience with customer projects and numerous service visits, it is possible to create a fairly accurate list of recurring errors. Each of them can be easily avoided with a bit of attention:

Mixing up the supply and return manifold – the system may work, but inefficiently, and thermostatic valves will operate in reverse
Loose fittings – with PEX pipes, a leak may occur that only becomes visible after the system is embedded in the floor
Skipping pressure testing – a fatal error; repairs will cost many times more than the test itself
Using an undersized distributor – for example, a 3-way when a 5-way is needed, leading to double feeding of rooms on one loop and no possibility of individual regulation
Missing loop labeling – during a failure or renovation, no one knows which loop belongs to which room
Mounting the distributor too low – flow meters become inaccessible or covered by the floor
Improper air venting – air remains in the system, the pump makes noise, and flow is low
Skipping hydraulic balancing – the most common cause of complaints such as "floor heating does not work well"

If you encounter problems during operation, also read the article Common problems with stainless steel distributors – leakage, weak flow, noise, where these situations are systematically addressed.

Material aspects of installation – why connection quality matters

Stainless steel distributors have a significantly longer lifespan than brass ones – corrosion practically does not threaten them even in more aggressive water. On the other hand, precisely for this reason, it is worth paying attention to the quality of each connection, because even secondary materials (gaskets, fittings, pipes) must be of the same level. It makes no sense to have a high-quality stainless steel distributor if you use cheap compression fittings with soft gaskets that last 5 years instead of the planned 30.

Always use gaskets made of EPDM or silicone, not cheap rubber. Check the compatibility of fittings with your type of pipe (PEX-A, PEX-B, PE-RT have different wall hardness and not all compression fittings are equally suitable). If in doubt, prefer press-fit or welded connections – these are technically superior to compression fittings in long-term operation.

The material comparison between stainless steel and brass is also covered in the article Stainless steel vs. brass distributor – which material is better for floor heating.

Distributor for a small apartment vs. a large family home

Installation-wise, each project is a bit different. For an apartment with two rooms and a bathroom, a 3-way stainless steel distributor is sufficient – one loop for each room. Installation is quick, the cabinet is small, and a skilled DIY enthusiast with professional support can manage it (of course, pressure testing and boiler connection should be entrusted to a professional).

In a family home with five rooms and a bathroom, the situation is different. Loops can be 80–120 meters long each, the total flow in the system is high, and hydraulic balancing is essential. In this case, we recommend considering professional installation from the start or at least consulting with a professional before beginning. The cost of professional balancing (4–8 hours of work) is a fraction of what it would cost to fix problems caused by poor settings after a year of operation.

Frequently asked questions (FAQ)

Do I need to turn off the entire heating system in the house when installing a distributor?

Yes, before connecting the distributor to the existing system, you must close the main shut-off valve and ideally drain the water from the part of the system you are working on. Working on a pressurized system is dangerous and the outcome is uncontrollable. If you are installing a distributor in a new building where the system is not yet filled, this step is not necessary, but still applies – fill the system only after all connections are completed.

What is the correct operating pressure for floor heating?

The standard operating pressure in a closed floor heating system is 1.5 to 2.5 bar in the cold state. After heating the water and expansion of the fluid, the pressure will rise slightly – usually by 0.3–0.5 bar. The expansion tank must be properly oversized to ensure the pressure does not exceed the safety valve setting (standard is 3 bar). The manometer on the distributor allows you to monitor these values continuously.

Can I use one distributor loop for two rooms at the same time?

Technically yes, but in terms of regulation, it is a disadvantage – both rooms will always be turned on or off together, with no possibility of individual settings. If the rooms are similar in size and have the same heating demand (e.g., two identical children's rooms), the solution is acceptable. If it is a bathroom and a living room – with significantly different needs – it is always better to assign each room its own loop. Therefore, it pays off to choose a distributor with a higher number of outputs from the beginning when planning.

What is the maximum recommended volume (length) of one loop?

For PEX pipe Ø16 mm, the maximum recommended length of one loop is around 80–100 meters. With a longer loop, hydraulic resistance increases to such an extent that a standard circulation pump cannot maintain sufficient flow. If you need to cover a larger area, divide it into two shorter loops. The rule is: better two shorter loops with even flow than one very long one with insufficient circulation.

What to do if pressure drops during a pressure test, but no leak is visible?

If the pressure drops, but no bubbles appear in the soapy water on the fittings, there are two possible causes: either the air in the system is compressing and now being released (apparent drop), or there is a leak in a place you cannot see – for example, in a pipe that is partially covered. Let the system stabilize for 60 minutes at the test pressure – if the drop stops or slows down to less than 0.1 bar per hour, it is typically just elastic deformation of the PEX pipes. If the drop continues constantly, systematically isolate sections by closing loops one by one and measure where the pressure is lost.

Is distributor installation a job for a DIY enthusiast, or only for a professional?

It depends on the scope. Mounting the distributor into the cabinet, securing it, and connecting the loops can be done by a skilled DIY enthusiast with technical thinking – if they prepare thoroughly and proceed systematically. The pressure test and documentation should be verified by a professional. Connecting to the boiler, installing the expansion tank, safety valve, and electrical connections for actuators and thermostats must be done by the appropriate professional – a gas technician for a gas boiler, an electrician for the electrical part. Money saved on a "skilled neighbor" will quickly disappear in the event of a failure.

Conclusion

Installing a stainless steel distributor for floor heating is a project you can handle – if you approach it systematically, with good preparation and without shortcuts. The key points of the entire process are three: choosing the right product before installation, conducting a thorough pressure test before embedding the floor, and hydraulic balancing after startup. Skipping any of these steps will come back to you – either immediately in the form of a leak, or later in the form of cold rooms and high energy bills.

Stainless steel distributors are an excellent investment in this context – durable, hygienically safe, and long-lasting. Whether you choose a 2-way for a small apartment or a more extensive 5-way distributor for a larger home, the installation procedure remains the same – only the scope of work and the time needed for setup change. The rules of professional installation apply equally, regardless of the project size.

Do you have a question on this topic?

Having trouble making a decision or dealing with a specific situation at home? Write to us - we are happy to help.