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Frozen condensate pipe
Checked against its sources: Updated
A frozen condensate pipe shuts a condensing boiler down in cold weather, and Worcester and Ideal user guides allow a thaw at ground level with warm, never boiling, water.12 Above ground level it is an engineer's job.
- Covers
- Condensing boilers in the UK. Each set of steps applies only to the maker named.
- You
- Where your maker's guide allows it, thaw an easily reached pipe at ground level, then reset once.
- A professional
- Any pipe above ground level, any rerouting or freeze protection, and any boiler that will not restart.
1 What a frozen pipe does
Worcester says a frozen or blocked condensate pipe will shut the boiler down, and that pipework run outside or through an unheated space such as a garage can freeze even when well insulated1. Ideal describes a gurgling noise before the display shows "Ignition Lockout" on the Logic+, and again after a reset3.
Baxi's newer quick guides give their own codes: E.04.10 on the 400, 600 and 800 Combi 2, and E133 on the Compact guide45. The same E133 means a gas supply interruption or flame failure in the Baxi Platinum guide, so a code only counts for the manual it came from7. See reading a fault code.
Stay on the ground. Worcester says never to attempt a thaw on a pipe at height, and Ideal says not to attempt pipework above ground level, so a pipe that needs a ladder is a job for an engineer. Boiling water can damage plastic pipe, and water left on a path can refreeze into a slip hazard. Nothing here involves going inside the boiler.
2 What each maker tells users
| Maker | What the document says |
|---|---|
| Worcester | Detailed thaw steps, ground level and easily accessible only. The Greenstar i ErP guide is an exception: it gives no steps and says to contact Worcester112 |
| Ideal | Detailed steps, not above ground level. If not competent, call a Gas Safe installer23 |
| Baxi | Quick guides call it an easy problem and point to a video, with no steps or height warning in the document45. Steps appear only on Baxi's website, not in the user documents read6 |
| Vaillant | Check the discharge pipe and tundish regularly; have any fault put right by a competent person. No thaw steps in the manuals read; see Vaillant's video below8 |
| Glow-worm Energy7 | Same instruction to use a competent person. No thaw steps9 |
| Viessmann | The word "condensate" does not appear in the two user documents read1011 |
3 Worcester's steps
From the Greenstar 4000 manual, for a pipe at ground level that is easy to reach. Follow the guide for your own model.
- Find the blockage as closely as possible, usually the most exposed point outside1
- Apply a hot water bottle, a microwaveable heating pack or a cloth soaked in hot water to the outside of the pipe, close to the blockage1
- Water can also be poured on from a watering can. The manual's words are "hot water, but not boiling"; Ideal and Baxi say warm, and warm is the safer reading1
- Reset the boiler and wait two or three minutes. If it does not restart, contact Worcester1
4 Ideal's steps
From the Logic Combi guide and the Logic+ guide of May 2014. These are older issues, and the current revisions could not be obtained23.
- Follow the plastic pipe from the boiler to its end and find the frozen point2
- Apply a hot water bottle, microwaveable heat pack or warm damp cloth; several applications may be needed2
- Warm water can be poured from a watering can. Do not use boiling water2
- Once the pipe flows freely, reset the boiler. If it fails to ignite, call a Gas Safe registered engineer3
5 Baxi's web advice
Baxi's FAQ page says to switch off at the control panel and the wall, find the frozen point, warm the exposed pipe with a hot water bottle, heat pack or warm water from a watering can, then restore power and restart6. Boiling water is ruled out there. The page states no height limit, so the ground-level rule above should still be applied. Its code list also varies from the manuals, so do not rely on it to identify a fault67.
6 After the thaw
Reset once, using the method in the manual for your model, because methods differ between makers; see resetting a boiler. Worcester says to ask the installer for a permanent solution1. An industry leaflet endorsed by the Heating and Hot Water Industry Council prefers an inside drain route; failing that, a product that guards against freezing13. For cold spells, Ideal suggests the boiler thermostat at maximum, heating on continuous and the room thermostat at 15°C overnight or when the house is empty, all returned to normal afterwards3. More on the pipe itself is under condensate pipe.
From the VaillantUK channel on YouTube. Vaillant's video, for Vaillant boilers, shows warm water, not hot, or a hot water bottle. Keep to easily reached ground-level pipe. Nothing loads from YouTube until you press play.
Sources
- Frozen pipe section, pp16-17, Greenstar 4000, Worcester document 6720891170, issue 2020/09 read 3 November 2026.
- Logic Combi 24, 30, 35 Users Guide, Ideal, 2013 file, p4, third-party copy read 3 November 2026.
- Logic+ Combi 24, 30, 35 User Guide, Ideal, UIN 204979 A07, May 2014, p12, seen on a third-party host, read 3 November 2026.
- Baxi Combi 2 range quick start, 7876395-01, p10 read 3 November 2026.
- Compact quick guide user instructions, Baxi, 7849761, p2 read 3 November 2026.
- Error codes and frozen condensate FAQ, Baxi website, not a user manual read 3 November 2026.
- Platinum Combi User Guide, Baxi, 7697821-01 (1/18), p8 read 3 November 2026.
- ecoTEC plus operating instructions, Vaillant, 0020308119_03, 28.11.2023, p16 read 3 November 2026.
- Energy7 combi operating instructions, Glow-worm, 0020300878_00, 02.03.2020, p12 read 3 November 2026.
- Vitodens 050-W user instructions, 6173895, 05/2026 read 3 November 2026.
- Vitodens 100-W/111-W user instructions, 6167584, 03/2026 read 3 November 2026.
- Worcester i ErP guide, 2015/03, p26 read 3 November 2026.
- Frozen boiler condensate discharge leaflet, HHIC-endorsed, Issue 1.0, October 2018 read 3 November 2026.