Underfloor Heating Systems Ltd has designed and supplied warm-water underfloor heating since 2002, supporting thousands of UK plumbers with ready-to-install kits and technical advice.
Quick Reference
- Incorrect pipe spacing
- Too little sub-floor insulation
- Skipping the pressure test
- Kinking pipe on tight bends
- Poor manifold siting and oversize loops
- Wrong pump speed / flow setting
- Rushing screed curing and first heat-up
1 | Pipe Spacing That Doesn’t Match the Heat Loss
Problem – Spacing the pipework at a uniform 200 mm in a north-facing orangery leaves chilly stripes, while 75 mm centres in a well-insulated lounge waste materials and pump head.
Fix – Use 100 mm centres for rooms over 50 W/m² heat loss and 150 mm for modern, low-loss zones. Every Single Zone 10 m² Kit ships with 16 × 2 mm multilayer pipe, clip rails and an illustrated layout guide that shows the correct centres for each room type.
See kit: 10 m² One-Zone Kit
2 | Under-Specifying Insulation
Problem – Heat is driven into the slab instead of the room, forcing higher flow temperatures.
Fix – Follow Part L guidance: at least 100 mm PIR/EPS below the pipe on ground floors, plus perimeter edging strip to allow screed expansion. All kits arrive with 300 pipe clips per 10 m², so you can clip securely through thick insulation without extra spend.
3 | Forgetting the 6-Bar Pressure Test
Problem – A pin-hole nicked by a trowel shows up only after the screed sets.
Fix – Before screeding, cap the flow and return on the control unit, fill with water and pressurise to 6 bar for at least 2 hours. The mixing unit included with every kit has integral fill-and-flush valves plus a 0–10 bar gauge, so no extra gear is required.
4 | Kinks from Over-Tight Bends
Problem – A 16 mm multilayer pipe should never be bent tighter than a 100 mm radius; do so and the aluminium layer can crease, throttling flow.
Fix – Walk the coil off a decoiler, keep bends gentle and switch to a spiral (“snail”) pattern in tricky corners. If a kink does occur, cut out the damaged section and use a certified press or compression coupling.
5 | Putting the Manifold in the Wrong Place
Problem – A control pack jammed behind the cylinder cupboard forces every loop to run an extra 10 m, increasing pressure drop.
Fix – Mount centrally on the zone wall where possible and keep loop lengths ≤ 100 m. The Nordic Pro Dual Zone 25–30 m² Kit uses a two-circuit manifold with flow regulators and a Grundfos UPM3 pump, making balancing straightforward even when the manifold has to sit off-centre.
See kit: Nordic Pro 2 25–30 m² Dual-Zone
6 | Incorrect Flow Rates
Problem – Undershooting the design flow leaves the loop furthest from the pump cool.
Fix – For 16 mm pipe, aim for 2.0–2.5 l/min on a 100 m loop. A quick rule from our design guide: Divide loop length by 40 to get the target flow in l/min. Set the Grundfos UPM3 to speed III during commissioning, then drop to the lowest speed that still achieves design temperatures to save running costs.
7 | Screed Cured Too Fast — or Not Long Enough
Problem – Lighting the boiler a week after pouring can crack a cement screed; leaving heat off for months delays client sign-off.
Fix – Let cement screed cure one day per 2 mm thickness (≈ 65 mm screed ≈ 33 days). Bring flow temperature up by 2–3 °C per day from the minimum mixer setting until the room reaches design set-point. Questions about fibre or liquid screeds? Call us on 01905 354 791.
Handy Checklist
- ≥ 100 mm insulation installed
- Manifold positioned centrally; loops planned ≤ 100 m
- Pipe clipped at 100–150 mm centres
- Pressure test to 6 bar passed
- Screed poured to manufacturer’s depth
- Gradual heat-up followed
Final Word
Avoid the seven mis-steps above and every underfloor heating job becomes a profit-maker, not a call-back. Ready to start? Browse the full range of single and dual-zone underfloor heating kits or call 01905 354 791 for same-day design advice.