There is no single right place for a radiant floor heating manifold. You choose it by weighing three things together: the leaders from the manifold to each room, the loop-length limit of your tubing, and access to the cabinet. A central location shortens the leaders, but that is only one of the three.
To see how much the location changes, we put the manifold in two places on one demonstration floor and let HeatAlgo calculate both, with every other input the same. Below are the results, what they do not show, a section on the usual US choices (basement, closet, one manifold per floor) and a worksheet for comparing two locations in your own home. If you are still collecting plans and product details, start with the radiant floor heating quote checklist.
What the manifold location decides
- The leaders to each room. Every loop has its own pair of leaders to the manifold, a supply and a return, so each foot between the manifold and a room adds about two feet of tubing to that loop. The tubing spacing and loop length guide explains why the leaders count toward the loop's length.
- Whether the longest loop stays within your tubing's limit. Each tubing manufacturer publishes a maximum loop length, leaders included. A loop that would go past it has to be split in two, and the second loop needs its own ports on the manifold.
- The tubing that passes through halls and doorways on the way, and the heat it gives off there.
- The cabinet itself: a wall that can carry it, room below the manifold for the tubing to bend up, and access for service once the house is furnished.
Basement, closet or one manifold per floor?
These are the three questions US homeowners ask most. A homeowner on HeatingHelp asked "Should manifold be on second floor?" or stay on the floor below. Others want the manifold in the basement, because it is easy to reach there. The trade-offs are the same ones as on the demonstration floor below, just stacked vertically.
- In the basement mechanical room. Close to the boiler or heat pump and easy to service. The cost is length: every loop on the floor above needs a pair of leaders from the manifold up through the subfloor to its room, and the farther the room, the longer the loop. Ask how the installer will purge air from loops that rise above the manifold.
- In a closet or wall cabinet on the heated floor. The leaders stay short, and one supply and return pair carries the water from the heat source to the manifold. That pair is a single run, not one per loop. The closet needs a wall that can carry the cabinet, room below the manifold for the tubing to bend up, and a door that opens with the house furnished.
- One manifold per floor. Where each floor has its own radiant loops, a manifold on each floor keeps that floor's loops short and leaves only the supply and return pairs running between floors. Whether you need two depends on the number of loops, the tubing manufacturer's loop-length limit and where a cabinet can go on each floor.
The demonstration below compares two positions on one floor. The method is the same for basement against closet: draw each loop's leaders to each candidate, add them to the loop, and compare the longest loop with the limit.
One floor, two manifold positions
We used the fictional Cedar House main floor from our radiant floor heating design guide: a 32.8 × 26.2 ft (10 × 8 m) single-story plan with a living and dining room, a kitchen, a bedroom and a hall between them, heated by eight loops. In position A the manifold stands at the end of the hall, where that guide's demonstration report has it. In position B it stands on the hall wall halfway along, opposite the living-room door.
Everything else stayed the same: the rooms and their heat losses, the eight loops and their tubing spacing, 16 mm (5/8 in OD, the size of 1/2-inch PEX) tubing under 1.8 in (45 mm) of concrete, ceramic tile, and a design supply and return of 109/100 °F (43/38 °C). Each pair of leaders also leaves its room at the same point in both positions, so the loops inside the rooms are identical and every difference below comes from the leaders through the hall.
Position A is where the demonstration put the manifold, with its leaders as they were drawn then. Position B is ours: we placed the cabinet so its ports line up with the living-room leaders, and drew the eight new leader pairs so that none cross. In both positions the tubing leaves every room through its doorway; where tubing can pass through a partition next to the manifold, both positions would give different leaders.
The in-room loops were calculated by the app as it stood on 24 September 2026. Since that day the kitchen loop 0/3/B has bends with the radius they need and comes out 5.6 ft (1.7 m) longer than in the demonstration report. That is why position A takes 1,261.5 ft (384.5 m) of tubing here, while the demonstration report of 20 September 2026 gives 1,255.9 ft (382.8 m). Every other loop is the same.
The demonstration report used 102/93 °F (39/34 °C). HeatAlgo now evaluates tile at the covering resistance EN 1264-3 takes for dwellings, and at that value this floor needs a supply water temperature of 108 °F (42.2 °C), which the report rounds up to 109 °F (43 °C). Both runs therefore use 109/100 °F, and every room is covered in both.
Position A, end of the hall: the manifold is against the end wall. The leaders of all eight loops run side by side along the hall from the living-room door to the cabinet. Position B, halfway along the hall: the manifold is on a side wall opposite the living-room door, in a 4.6 ft (1.4 m) wide hall. The kitchen leaders come down the hall, the living-room leaders cross it and the bedroom leaders come up it, in short bundles.
What HeatAlgo calculated
| Result (fictional Cedar House floor, calculated 23 September 2026) | A: end of the hall | B: halfway along the hall |
|---|---|---|
| Leaders of all loops (supply and return) | 284.8 ft (86.8 m) | 169.3 ft (51.6 m) |
| Tubing inside the heated sections | 977.0 ft (297.8 m) | 977.0 ft (297.8 m) |
| Tubing in total | 1,261.5 ft (384.5 m) | 1,146.0 ft (349.3 m) |
| Longest loop, leaders included | 0/1/C, 184.1 ft (56.1 m) | 0/3/A, 179.8 ft (54.8 m) |
| Loops above HeatAlgo's 262 ft (80 m) warning for 16 mm tubing | none | none |
| Flow of all loops together | 1.98 gpm (450.5 l/h) | 1.98 gpm (450.5 l/h) |
| Warnings in the app | none | none |
Loop by loop, in feet (converted from the metric lengths the app reports):
| Loop | Leaders A | Loop A | Leaders B | Loop B |
|---|---|---|---|---|
| 0/3/A (kitchen) | 12.8 | 176.5 | 16.1 | 179.8 |
| 0/3/B (kitchen) | 16.7 | 104.0 | 10.5 | 97.8 |
| 0/1/A (living) | 50.2 | 161.1 | 35.1 | 146.0 |
| 0/1/B (living) | 31.8 | 139.4 | 18.4 | 126.3 |
| 0/1/C (living) | 52.5 | 184.1 | 35.4 | 167.0 |
| 0/1/D (living) | 37.7 | 166.3 | 18.7 | 147.3 |
| 0/4/A (bedroom) | 39.4 | 163.1 | 14.1 | 138.1 |
| 0/4/B (bedroom) | 43.6 | 167.3 | 20.3 | 144.0 |
| Total | 284.8 | 1,261.5 | 169.3 | 1,146.0 |
Moving the manifold halfway along the hall cut the leaders from 284.8 to 169.3 ft of tubing, 115.5 ft (35.2 m) less, and the tubing in total by about 9%. Seven of the eight loops got shorter, by 6.2 to 25.3 ft (1.9 to 7.7 m). One got longer: kitchen loop 0/3/A, by 3.3 ft (1.0 m), because its leaders leave the kitchen above position B on the plan and now run down the hall instead of up it. The longest loop, the one that counts against the limit, changed least: 4.3 ft (1.3 m) shorter, and at B it is a different loop. No loop came near the 262 ft from which HeatAlgo warns about a 16 mm loop. Totals and differences are worked out before rounding, so the rounded rows can differ from them by up to 0.7 ft (0.2 m).
The flows did not change. HeatAlgo sets each loop's flow to EN 1264-3 as G = 0.86 · (Q + Φ_FB) · (1 + Ro/Ru) / σ: Q is the output the loop gives the room, Φ_FB its share of the heat lost downward through the floor (split between the room's loops by area), and σ the temperature drop along the loop. None of these depends on where the manifold hangs. The loop outputs, the room balances and the required supply water temperature were the same in both positions too. These are calculated values for a fictional floor, not measurements of an installed system.
What the numbers do not show
- Pressure drop and balancing. Water loses pressure along the tubing, so a longer loop asks more of the circulator, and loops of similar length are easier to balance against each other - Wavin's manifold guidance links short loops to a balanced system. HeatAlgo does not calculate pressure drop. Ask your installer which loop is the most demanding and how the others will be set on the manifold.
- The heat from the leaders. HeatAlgo counts every leader in its loop's length, but not the heat it gives off on the way, and the hall in this example has no loop of its own. At A the leaders of all eight loops run side by side up the hall; at B they arrive from three directions and meet at the cabinet. Where tubing bunches together, Grant's installation guide advises insulating it so the floor does not overheat, especially if it is not meant to heat the space it passes through. Whether the leaders should warm the hall is a design decision, not a by-product.
- The cabinet and its wall. Position B puts the cabinet on a side wall halfway along a 4.6 ft wide hall, where a surface-mounted cabinet takes about 5.5 in (14 cm) of its width; position A keeps it against the end wall. On this plan position B sits where the kitchen-bedroom wall meets the hall wall, so only a surface-mounted cabinet fits there, and position A is on an exterior wall - ask your builder before recessing anything into it. The partitions on this plan are 4.7 in (12 cm) thick, so check the depth of a recessed cabinet against the wall before choosing one.
- Room below the manifold. The tubing needs room to bend up into the lower bar. Grant's guide, for example, asks for at least 11.8 in (300 mm) from the floor to the lower (return) manifold. Follow the instructions for the manifold and cabinet you buy.
- Your own house. This is one fictional single-story floor. Your loops, distances and tubing give different numbers, and on a plan with long leaders, such as a basement manifold feeding the floor above, a loop can pass its limit where none did here. HeatAlgo calculates floors with the tubing embedded in a slab or thin slab (type A in EN 1264). It does not calculate joist-space, staple-up, plate or panel systems; for those, ask the system's manufacturer for output data.
Compare two locations on your own plan
Mark both candidates on your plan, then answer the same questions for each. Copy the table into a spreadsheet or print the page. A blank answer is a question for your installer, not a no.
| Question | Location A | Location B |
|---|---|---|
| Where exactly the cabinet goes, and on which wall (basement, closet, hall) | ||
| Surface-mounted or recessed, and whether the wall can take it | ||
| Room below the manifold for the tubing to bend up into it | ||
| Access for service, with doors open and furniture in place | ||
| Route of every loop's leaders to the manifold, drawn on the plan, including any run through the subfloor | ||
| Longest loop, leaders included, against the tubing manufacturer's limit | ||
| Ports needed, spares included, against the manifold's size | ||
| Where tubing bunches together, and whether it is sleeved or insulated | ||
| Power and wiring for the actuators and room thermostats | ||
| Supply and return to the heat source, filling and purging air |
What you can check in HeatAlgo
In HeatAlgo you draw the heated sections on your plan, place the manifold and draw each pair of leaders from its room to the manifold. The app shows each leader pair's length and each loop's length with its leaders. It flags a 16 mm loop longer than 262 ft (80 m) and treats 295 ft (90 m) as its limit; for 17 mm tubing the figures are 295 and 328 ft (90 and 100 m). These are the app's warnings; your tubing manufacturer's published loop length is the one that applies to your job. When you move the manifold, the app keeps the path you drew for each leader, moves only its end with the manifold and recalculates the lengths. To compare two locations fairly, redraw each leader along the way the tubing would really go to the new location, as we did for position B. HeatAlgo does not calculate pressure drop or the heat the leaders give off.
On a free account, with no card required, you can draw the whole floor and see the building summary and one fully calculated room. The paid report unlocks the other rooms' results, including their leader and loop lengths, and the printable plan. A report is a basis for the conversation with your installer, not an approved design: it does not include a site visit, installation or sign-off.
For what else to bring to that conversation, see the radiant floor heating design guide or the radiant floor heating overview.
Draw your floor and compare manifold locationsA HeatAlgo report follows EN 12831-1 and EN 1264, not ACCA Manual J, and is not accepted for permits or rebates.