Heating upstairs but not downstairs: circulation and balancing checks
Quick answer
Heating that works upstairs but not downstairs (or vice versa) is usually about how hot water is distributed around the system, not a thermostat fault. Check whether all downstairs radiators are affected, confirm valves are open, and try a simple flow test by turning down a few very hot radiators elsewhere. If the imbalance persists or several radiators are affected, a heating engineer can properly balance the system.
Safety first
- Don’t force valves or attempt internal boiler work.
- If you hear loud banging/overheat symptoms, stop and get help.
- Smell gas or suspect a leak: ventilate, leave the area, and call 0800 111 999.
- CO alarm sounding or anyone unwell: get fresh air and get urgent help.
Full checklist: Safety guidance
What you may notice
- All downstairs radiators stay cool while upstairs heats fine — may suggest a distribution or flow restriction issue affecting that part of the system.
- Downstairs pipes near the valves don’t get warm at all — can point to restricted flow reaching that circuit.
- Downstairs heating improves once you turn down some very hot upstairs radiators — this suggests a balancing issue, where one part of the system is taking most of the available flow.
These are possible explanations, not a confirmed diagnosis. An engineer can confirm the exact cause on inspection.
Safe checks to make, in order
- Confirm which radiators are affected (all downstairs or only some).
- Check downstairs TRVs are open and pins not stuck (gentle).
- Feel downstairs flow pipes near valves: do they get warm at all?
- Temporary test: turn down a few very hot upstairs radiators to see if flow shifts downstairs.
- If sealed: check system pressure; note any pressure or air issues.
What you can do safely
- Check whether all downstairs radiators are affected or only some of them.
- Open downstairs TRVs fully and confirm the pins are free.
- Turn down a few very hot upstairs radiators to test whether flow redistributes.
- Check system pressure if you have a sealed system.
When to call a professional
- You need proper balancing across many radiators.
- Signs of sludge/dirty water, repeated bleeding, or noisy pump/boiler.
- Any leaks or pressure instability.
What to tell the engineer
- Which of the checks above you carried out, and what you found at each step.
- Roughly when the problem started and whether it’s constant, intermittent, or linked to specific conditions (e.g. only when heating runs, only in cold weather).
- Any fault code, unusual noise, or visible sign you noticed.
- Whether the issue affects one fixture/radiator or several.
FAQs
Why would only one floor be affected?
Central heating systems distribute hot water around a circuit, and if one branch (such as upstairs) is taking more flow than it should, other branches can be starved. This is often a balancing issue rather than a fault with any single radiator.
Is this the same as one radiator not heating?
It’s a related but broader version of the same underlying idea — flow distribution. See our guide on one radiator not heating if it’s isolated to a single radiator rather than a whole floor.
Can I balance the whole system myself?
Balancing an entire heating system properly usually benefits from a professional’s tools and experience, especially across many radiators. Basic checks like TRVs and lockshields being open are safe to do yourself first.
Could this be a pump problem instead?
It’s possible — a struggling pump can also affect distribution across a system. This is something a heating engineer can assess alongside balancing.
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