Heating upstairs but not downstairs: circulation and balancing checks
Quick summary
If upstairs heats but downstairs doesn’t, it’s usually flow distribution or restriction — not a thermostat issue.
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 to check (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 the result means
- Downstairs pipes stay cold: distribution/flow restriction or pump head issue.
- Flow improves when upstairs throttled: balancing issue (upstairs taking most of the flow).
- Some downstairs rads warm weakly: partial restriction/sludge or long-run losses.
What you can safely do
- 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.
Engineer notes
Map circuit resistance. Check pump setting and bypass arrangement. Look for short-circuiting upstairs (open lockshields/TRVs) starving distant circuits. Temperature mapping and systematic balancing (lockshield turns recorded) is key. For older microbore, consider distribution limits and restrictions; assess water quality and filter status.
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