Frequently Asked Questions About Brass Manifolds

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A brass manifold is one of those heating system parts an average homeowner thinks about exactly twice in their life – when building or renovating a house, and when, years later, something starts to drip. In between, it works quietly in a cabinet under the plaster or in a utility room and nobody pays it any attention. That's exactly why a lot of questions have accumulated around it, questions that reach us both through our advice desk and in discussions under products – from choosing the right type, through how it's installed and set up, to what to do when it starts dripping or when one circuit doesn't heat as well as the others. In this article we've collected the most common questions customers ask us about brass manifolds, and we answer them practically, without unnecessary theory – the way we'd explain it to a neighbor doing their own underfloor heating installation.

What exactly is a brass manifold and what is it for

A manifold (more precisely a distribution and collection set, in Slovak often just called "rozdeľovač/zberač") is a fitting that distributes heating water from a single main pipe (from the boiler or from the main riser) into several separate circuits – underfloor loops, radiator branches, or a combination of both. It always consists of two parallel pipes: the upper distribution pipe (supplies hot water to the circuits) and the lower collection pipe (returns the cooled water back to the boiler). Brass is used for manufacturing because it handles temperatures up to approximately 110 °C well, the typical operating pressure of heating systems in family houses (usually up to 6 bar, the fittings themselves usually withstand considerably more – a maximum operating pressure of around 10 bar is commonly stated), and it resists corrosion better than ordinary steel, though worse than stainless steel, as discussed below.

Practically every brass manifold on the market has the same connection principle: a main inlet and outlet with a 1" external thread (most commonly), and individual circuits with an EK-type connection (Euroconus, 3/4" thread) for direct connection to Euroconus fittings or connecting hoses/pipes. The spacing between individual circuits is standardized at 50 mm on the vast majority of brass manifolds – this is important to know especially when you're buying brackets, a cabinet, or accessories from a different manufacturer than the manifold itself, because it's precisely thanks to this uniform spacing that parts from different brands are largely compatible.

Basic wiring diagram

The following diagram shows how the manifold fits into the whole system – from the boiler, through the main pipe, to the individual underfloor heating or radiator circuits.

Questions before buying

How many circuits on the manifold do I actually need?

This is by far the most common question we deal with, and the simple answer is: one to two circuits more than what's currently needed according to the project. The reason is practical – buying a separate manifold for one additional circuit later (for example when you decide to add a radiator to the garage or extend the underfloor heating into a conservatory) is more expensive and spatially inconvenient than having one or two extra positions from the start. For a typical family house up to 120 m² with underfloor heating, you usually end up with 6 to 10 circuits (one circuit per room up to approximately 15–20 m², larger rooms are split into two circuits for even heating and because of loop length, which for a single long circuit would exceed the recommended approximately 100 m of pipe). The exact number of circuits is always part of the underfloor heating project – guessing isn't recommended, because an undersized manifold simply can't be "extended alongside" in the cabinet.

You'll find a detailed procedure for calculating circuits (including a sample calculation for a specific floor area) in a separate article, How many manifold circuits do I need.

What's the price difference between a 2-way, 3-way and multi-way manifold?

The price grows with the number of circuits, but not entirely linearly – the more circuits, the lower the price per circuit tends to be, because the manifold body, the shut-off ball valves at the inlet/outlet and the surface finish are "spread" over more positions. As a specific example, we can give the real prices of manifold/collector sets without a cabinet with a 1"xEK connection: a 2-way set costs €100.37, i.e. €50.19 per circuit, while a 3-way set costs €138.74, which works out to €46.25 per circuit. The difference isn't dramatic, but it gradually shows up with larger sets.

*The indicative price of a set for heating elements with a nickel-plated finish (€182.04) is given for comparison – this is a different type intended more for radiator circuits, not a direct equivalent to the first two sets.

EK connection or 1"? What's the difference?

This confuses almost everyone dealing with a manifold for the first time. The 1" (inch) thread is always on the main inlet and outlet of the manifold – water for all circuits combined flows through here, which is why it needs a larger diameter. EK (Euroconus, 3/4") is the connection for individual circuits – each circuit has a separate, smaller thread, because the flow in a single loop is considerably smaller than the combined flow of the whole set. So when you see "1"xEK" in a product name, it means the main connection is 1" and the circuit outlets are EK. This is exactly how our 1"xEK, 2-way manifold/collector set is labeled, for example.

Manifold/collector set - without cabinet - 1"xEK; 2-way; brass - a complete two-circuit set with a 1" main connection and EK outlets, exactly as described above, suitable for example for adding a separate circuit to a garage or extension. Price from €100.37.

Installation questions

Does the manifold have to be in a cabinet, or is it fine mounted freely on the wall?

Neither law nor standard directly requires a cabinet, but in practice it almost always pays off – it protects the manifold from mechanical damage, hides it visually, and above all makes later servicing easier (venting, flow adjustment, gasket replacement), because the cabinet usually has a door right at the level of the controls. Without a cabinet, the manifold is usually mounted on brackets directly on a masonry wall in a utility room, which is common especially for manifolds serving radiator circuits or in a basement. For more detail on choosing a suitable cabinet, see the article Cabinets for brass manifolds.

Whether you mount the manifold in a cabinet or on an open wall, it always needs firm fixing at two points (usually using double brackets with the exact 50 mm spacing mentioned above), so that no stress builds up on the connections during later tightening or thermal expansion of the pipes.

Mounting bracket - for manifold - 1 inch; 200mm; double

Mounting bracket - for manifold - 1"; 200mm; double - exactly this type of double bracket, with spacing matching the manifold standard, is used to firmly anchor it to the wall or into the cabinet frame, so the fitting doesn't put stress on the pipework during operation. Price from €7.22.

What pipe is connected to the circuits, and is anything special needed where it passes through a wall or under plaster?

Multilayer pipe (PEX-AL-PEX or PE-RT) with an outer diameter of 16 or 18 mm is most commonly connected to the manifold circuits, fitted at the end with a Euroconus (EK) fitting screwed directly into the manifold outlet. Where the pipe passes through a wall, an expansion gap in the floor, or runs freely outside the screed for a short section (for example the run from the manifold to the first bend in the floor), it's recommended to slide on a protective corrugated hose. This serves two functions – it mechanically protects the pipe from damage during later construction work, and at the same time allows the pipe to shift slightly with thermal expansion without pulling directly on the connection at the manifold.

Protective hose for pipes 16-18mm - blue - suitable exactly for pipe sections passing through a wall or an expansion gap right next to the manifold, protects against mechanical damage and allows for expansion. Price from €31.00.

We describe the complete step-by-step installation procedure, from preparation through connection to the pressure test, in the article Installing a brass manifold. In short, this is the sequence of steps:

How long should the pressure test last and what should I watch for?

Common practice is to pressurize the system to a value higher than the actual operating pressure will be (typically a test pressure of about 1.3 times the operating pressure is used, so for a typical operating pressure of around 3-4 bar in a family house, the test pressure is usually somewhere around 4-6 bar) and leave the system like this for at least several hours, ideally overnight, before the screed is poured. You're watching for two things: whether the pressure on the gauge drops (indicating a leak somewhere in the system), and you visually check every connection on the manifold and on the EK fittings for any sign of a drip. Only after a successful test may the pipework be covered with screed – repairing a leaking joint after pouring is significantly more complicated and expensive.

Operation and setup questions

Why does one circuit heat less than the others?

This is the second most common question after the number of circuits. There are usually three causes: (1) the circuit is longer than the others and therefore has higher hydraulic resistance, so it needs the flow valve on the manifold opened more, (2) there's air in the circuit blocking water flow, (3) the flow valve (rotameter) on the given circuit is throttled more or less than it should be given the loop length. The solution is always the same – first thoroughly vent the circuit, then check and, if necessary, readjust the flow so that longer circuits get proportionally greater flow. You'll find the exact procedure for setting flow on individual circuits, including indicative values by loop length, in the article Setting flow on individual circuits.

Can a separate temperature measurement also be connected to the manifold?

Yes, and it's a common and useful modification, especially where you want an immediate visual overview of the supply and return temperature without needing a digital meter. A T-piece with a built-in thermometer is simply inserted into the manifold's inlet or outlet instead of a regular straight T-piece – the installation is identical, just with an analog thermometer added directly in the fitting's body.

T-piece with thermometer - EKxEK - a simple way to have an immediate visual overview of water temperature right on the manifold, without needing to buy a separate digital meter. Price from €21.74.

Do I need a thermostat by the manifold too, or is a thermostatic head on the valve enough?

It depends on the type of control. If you control the whole system centrally (for example with a room thermostat in the main living room that switches the whole boiler or circulation pump), the manifold itself doesn't need any control of its own – the flow on the circuits is set once at commissioning and doesn't change afterward. If, however, you want to control individual rooms independently (for example set an underfloor-heated room differently than a bathroom), then a surface-mounted or room thermostat is fitted to the specific circuit or directly at the distribution point for the given radiator, controlling the actuator on that circuit's head. A surface-mounted thermostat is in practice often used precisely where there's no space or reason to intervene in the piping – it simply attaches to the pipe and measures its surface temperature.

AVANSA TH 2A surface-mounted thermostat - a simple solution for independently controlling a specific circuit without intervening in the piping, attached directly to the pipe behind the manifold. Price from €11.81.

Brass or stainless steel? A question that comes up sooner or later

Brass manifolds are still the most widespread in family houses, mainly for price reasons – with the same number of circuits, they come out noticeably cheaper than a comparable stainless steel version. With properly treated water (i.e. without extremely aggressive or very hard water), brass has a typical service life comparable to stainless steel, but with unsuitable heating water treatment (low pH, high oxygen content from frequent system refilling) it's more prone to so-called dezincification of brass – a phenomenon where zinc gradually leaches out of the alloy and the material becomes brittle. Stainless steel, by contrast, is practically immune to corrosion even with less-than-ideal water quality, which is the main reason stainless steel is preferred in industrial applications and systems with harder water despite the higher price.

If you're weighing a specific decision between materials for your case, we go into more detailed criteria (including when investing in stainless steel actually pays off) in the article Brass vs. stainless steel manifold.

Faults and maintenance questions

The manifold is dripping at the shut-off valve – is that serious?

A small drip right at the main ball valve (at the manifold's inlet or outlet) is most often caused by a worn or dried-out O-ring seal in the control lever, not a problem with the fitting body itself. In the vast majority of cases this doesn't require replacing the whole manifold – replacing the seal, or in a worse case the whole valve cartridge, is enough. A leak directly at a threaded connection (where a fitting or screw connection is installed) usually means the joint wasn't tightened enough or that the PTFE tape/hemp seal was damaged during installation – here, disassembling the joint and resealing it helps, not replacing the manifold.

How often should the manifold be checked and what does routine maintenance include?

The recommended frequency is at least once a year, ideally at the start of the heating season: check the tightness of all joints, vent the individual circuits (especially if the system stood idle over summer), verify that the flow settings on the rotameters haven't changed (this happens mechanically only very rarely, but it's worth checking) and visually check whether traces of greenish corrosion have appeared on the fitting's surface or at the joints, which could signal the onset of dezincification. A complete overview of the most common faults and their solutions (including how to distinguish ordinary minor dripping from a more serious problem) is in the article Most common faults of brass manifolds, and on the topic of long-term care also Maintenance and service life of a brass manifold.

Can a manifold be expanded with another circuit later?

Directly buying and adding one segment to an existing manifold body usually isn't possible – brass manifolds are manufactured as a single-piece body for a given number of circuits, not as a modular building-block system. If you need an additional circuit (for example for a later extension), the solution is either to replace the whole manifold with a larger one, or to add a second, smaller separate set (for example a two-circuit one) next to it, connected to the same main pipe. The second solution is usually cheaper and less invasive, which is why it's used more often in practice.

Accessories worth having on hand

Besides the manifold itself, it's worth having basic accessories prepared in advance – mounting brackets, protective hoses for wall passages, or possibly a T-piece with a thermometer if you want visual control over temperature without an additional meter. A complete overview of commonly used accessories, including recommendations on what you really need and what's just "nice to have extra", is in the article Accessories and add-ons for the manifold.

Frequently asked questions

Does the manifold always have to be horizontal, or can it also be mounted vertically?

Standard installation is horizontal (upper pipe supply, lower pipe return), because the vent valves and rotameters on the individual circuits are designed for this – they assume a horizontal position of the body. Vertical installation isn't common and in most cases isn't recommended without consulting the manufacturer, because it would make venting the circuits more difficult.

Is there a difference between a manifold for underfloor heating and one for radiators?

The principle is the same; the difference is mainly in the diameter of the circuits and whether the manifold has built-in flow meters (rotameters) directly in the body – for underfloor heating these are almost always included, because precise flow setting on long loops is key for even heating. Manifolds intended directly for radiator distribution sometimes don't have rotameters, because the flow is regulated more directly at the thermostatic heads of the individual radiators.

How much does a complete set cost including cabinet and accessories?

It depends on the number of circuits, the type of cabinet (recessed/surface-mounted) and the range of accessories. As a guide, the brass manifold/collector set alone without a cabinet costs €100.37 for 2 circuits and €138.74 for 3 circuits, to which you need to add brackets (from €7.22 each), a possible cabinet, and protective hoses for wall passages (from €31.00). The easiest way to put together an exact calculation for your specific number of circuits is to select the individual items directly in the e-shop, or write to us using the form below.

Can a manifold be bought separately without a cabinet?

Yes, most sets are sold separately without a cabinet – this is common especially when you're mounting the manifold on an open wall in a utility room, or when you already have a cabinet from a different manufacturer and just need to replace the fitting itself. Thanks to the uniform 50 mm circuit spacing, compatibility between brands is trouble-free in the vast majority of cases.

How do I recognize that I have an undersized manifold?

Typical symptoms are: visibly uneven heating between rooms despite correctly set flows, having to keep some circuits permanently fully open and still getting insufficient output, or a situation where you'd like to add another circuit and the manifold no longer has a free position. In such a case, it's worth considering replacing it with a larger set or adding a second separate set alongside the original.

Does the manifold need to be replaced during a renovation, or is it enough to just check the original one?

If the original manifold shows no visible corrosion or leaks and matches the current number and layout of circuits, there's usually no reason to replace it – brass fittings, with properly treated water, typically last many years of operation. Replacement is worthwhile especially when the renovation changes the number of circuits, when corrosion is visible on the body, or when you want to switch to a type with built-in rotameters for more precise flow setting.

Have a question on this topic?

Not sure what to decide, or dealing with a specific situation in your home? Write to us - we're happy to help.