What it means
What Frozen condensate is telling you
Every modern condensing boiler produces acidic condensate water that drains away through a plastic pipe. If part of that pipe runs outside and the temperature drops below freezing, it can block with ice.
The boiler detects that it can't drain, and shuts down. This is the single most common reason we get called out on the first hard frost of winter — and it's often something you can sort yourself in ten minutes.
You'll usually get a gurgling or bubbling noise from the boiler just before it locks out, and a fault code like Worcester EA or Viessmann F4.
Before you call
Safe checks you can do yourself
- Find the white or grey plastic pipe (usually 22mm or 32mm) leaving the house near the boiler
- Pour warm — never boiling — water slowly along the length of it, concentrating on any bends or the open end
- A hot water bottle or heat wrap held against the pipe also works
- Once thawed, reset the boiler once and it should fire normally
- Never use a naked flame, and don't do it if it means climbing on anything unsafe
Never remove the boiler casing or work on the sealed combustion chamber yourself — by law that’s Gas Safe registered engineers only. If you smell gas, call 0800 111 999 immediately.
How we fix it
What we do on the visit
- Condensate re-routed internally to a waste pipe wherever it's practical — the permanent fix
- Pipe upsized to 32mm and re-pitched so water can't sit in it
- External sections properly insulated with weatherproof lagging
- Trickle heater fitted where the run genuinely has to stay outside
How urgent is it?
Often a DIY fix. If it refreezes every cold snap, get the pipework corrected properly.
Costs
What a repair costs
Our diagnostic visit is £99 inc VAT and it comes off the bill if we carry out the repair. We give you a fixed price before touching anything — no hourly rates, no surprises on the invoice.
We’re Gas Safe registered, Which? Trusted Trader endorsed and rated 4.9 across 206+ reviews. We carry the common Worcester Bosch and Viessmann spares on the van, so most faults are fixed on the first visit rather than booked back in.
Common questions
Why does my condensate pipe freeze every winter?
Because it runs externally with too little fall, too small a diameter or no insulation. Those are installation faults, not bad luck, and they're fixable permanently.
Can I pour boiling water on it?
No. Boiling water can crack the plastic pipe and split fittings, turning a free fix into a repair bill. Warm water only.
How much to fix it permanently?
Re-routing or upsizing a condensate run typically costs £120–£280 inc VAT depending on access, and it stops the problem returning every winter.
Book it in
Get an engineer out
Step 1 / 5
60 second boiler quote
No callbacks unless you want one
What can we help with?
Pick the option that fits — we'll tailor the next questions.
More help
Other fault codes
Worcester Bosch
EA
No flame detected — ignition lockout
Worcester Bosch
E9
Overheat — the boiler has got too hot
Worcester Bosch
A1
Pump fault or poor water circulation
Worcester Bosch
C6
Fan fault — fan speed out of range
Worcester Bosch
D5
Control board or communication fault
Viessmann
F2
Temperature limiter — overheat lockout