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Boiler condensate pump

Updated: 22 October 2026

Your combi or system boiler sits in a cupboard whose floor is below the nearest soil stack, and the installer’s note mentions a pump because gravity cannot reach an internal drain. This page explains why that liquid is not air-conditioning water, what England’s drainage guidance expects, and why a mini that says boiler on amazon.co.uk is not approval. Ranks sit on the [condensate pump comparison](/hub/heating/condensate-pump). Fitting order sits on [how to fit a condensate pump](/hub/heating/condensate-pump/sub/condensate-pump-how-to-fit). Approved Document H applies to England. Scotland and Northern Ireland use their own handbooks. A qualifying purchase can earn a commission at no extra cost to you.

Your combi or system boiler sits in a cupboard whose floor is below the nearest soil stack, and the installer’s note mentions a pump because gravity cannot reach an internal drain.

Our top picks

Grundfos Grundfos Conlift1-LS

Best overall

Grundfos Grundfos Conlift1-LS
8.8/10about £71.28
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Aspen Pumps Aspen FP3349 Max Hi-Flow

Rank 2

Aspen Pumps Aspen FP3349 Max Hi-Flow
8.8/10about £85.00
View offer
BAOSHISHAN BAOSHISHAN QS-360L

Best value

BAOSHISHAN BAOSHISHAN QS-360L
6.0/10about £59.99
View offer
On this page
  1. 1.A pump is the second choice
  2. 2.Warm and acidic
  3. 3.Where the pipe should end
  4. 4.What these listings do not prove

A pump is the second choice

HHIC and Benchmark-style installer guides repeat the same order. Route condensate to an internal foul water point by gravity where practical, using a 22 mm pipe and a trap that keeps drain air out of the appliance. A pump is specified only when that internal gravity route is impractical and the boiler manufacturer names a pump solution. Pumps add electricity, noise, maintenance and a safety path that can lock the boiler out if the tank overfills. Homeowners sometimes treat a pump as an easy fix for a long external pipe. Guidance treats the external run as a last resort with larger bore, insulation and short exposure, because freeze blockages are common in UK winters. A pump in the airing cupboard does not stop an iced outdoor leg if the fault is outside. If you are unsure whether gravity already works, ask a Gas Safe registered engineer before you buy hardware. Checking the route is cheaper than returning the wrong class of pump.

Warm and acidic

HHIC material talks about roughly two litres an hour at around 30–40°C from condensing boilers, with acidity low enough that building guidance discusses pH 6.5 and lower and refers to BS 6798. The liquid is not neutral tap water. It attacks some metals and plastics if the wrong pump is fitted. Condensatepump.co.uk states that its small SK units are for air conditioning, not boilers. When MAJONMMERD or Yosoo lists boiler on a compatible-devices line without a pH range, that is a keyword on a mini spec. Grundfos Conlift PDFs quote pH floors and higher flow than 24 L/h minis. Those figures do not appear on amazon.co.uk ASIN B01NBHHD9G, where flow, head, voltage and pH cells are blank. Aspen’s FP3349 prints HVAC duty and 40°C max water temperature without a pH line.
Grundfos Grundfos Conlift1-LS

Testsieger

Grundfos Grundfos Conlift1-LS
8.8/10about £71.28
View offer

Where the pipe should end

Approved Document H paragraph 1.14 in England names 22 mm pipe, a 75 mm trap seal and discharge to an internal foul stack or other approved foul water system, with material choices that respect acidity. External termination is constrained and should be the exception: short, insulated, visible and maintainable, not a hidden hose to the garden. Discharging boiler condensate into a rainwater butt, soakaway or surface water system is not what that indoor foul-water preference describes. Neutralisers appear in some proprietary boiler pump families for oil or specific manuals. Do not assume any pump in this twelve-pack includes one unless the listing and manual say so. AirTech-UK’s bullets name condensing boilers alongside refrigeration, yet the page does not print a pH limit. Treat it like any other listing: evidence on the page plus engineer approval, not a bullet keyword alone.

What these listings do not prove

The amazon.co.uk table mixes twelve pumps from about £26 to £85. None replaces a boiler manual or a Gas Safe method statement. Grundfos Conlift1-LS carries the boiler-associated name and a strong review count, but performance cells are empty. Copying 600 L/h from a Conlift PDF onto the buy box creates the wrong expectation. QS-360L and QS-24L print air-conditioning kilowatts on horsepower fields. Those numbers describe indoor unit size, not boiler approval. Denash and YUKERMARB 100 L/h pumps cap lift at 2 m, which fails many risers to a stack. Budget 24 L/h units claim 10 m head with 0.07 L tanks and no reviews. Read best condensate pump with that filter in mind. Aspen is HVAC-led on the listing. QS-360L names an air conditioner on the spec line. Neither replaces a named boiler pump on an install sheet. Altering the condensate route, the boiler safety circuit or the boiler case is Gas Safe work on a gas appliance. The engineer’s card must cover boilers. When a fitted pump misbehaves, use condensate pump not working before you order a replacement.

Common questions

Does every combi need a pump?
No. Only where gravity to an approved internal termination is impractical and the manufacturer specifies a pump.
Why is boiler water different from air-conditioning water?
Temperature and acidity. Boiler condensate is warm and acidic enough that building and HHIC material treat materials and routing seriously.
Can I discharge into a water butt or a soakaway?
Not for boiler condensate under the indoor foul-water preference in England’s Approved Document H guidance.
What pipe size and trap does England’s guidance name?
22 mm pipe and a 75 mm trap seal are named in Approved Document H paragraph 1.14, alongside pH and BS 6798 references.
What if the only drain is outside?
External runs are a last resort with freeze and maintenance risk. Insulation and bore matter. A pump does not remove that risk.
Which listing in this set actually states a pH?
None print a pH cell on the amazon.co.uk extracts in this batch. Manufacturer PDFs off-site may, but not these buy boxes.
Who is allowed to alter the boiler connection?
A Gas Safe registered engineer for gas appliances. Do not bypass safety switches.
Will a pump stop a frozen external pipe?
No. Freeze blockages can occur on external pipework while the indoor pump is healthy. Fault-finding must include the outdoor leg.

Related pages

Condensate pump buying guide

Condensate pump

Best condensate pump: top pick and who should skip

How to fit a condensate pump: the sequence, then stop

Condensate pump not working: float, tube and freeze

Sources

Public UK and manufacturer sources named below. amazon.co.uk prices, stars and review counts on these twelve listings were taken from the listing files. Page updated October 2026.

  1. Approved Document H, drainage and waste disposal (retrieved 21 October 2026)
  2. HHIC condensate discharge installer guide (retrieved 21 October 2026)
  3. HHIC condensate pipe guidance news (retrieved 21 October 2026)
  4. Gas Safe Register FAQ (retrieved 21 October 2026)
  5. Aspen FP3349 tech sheet (retrieved 21 October 2026)
  6. Grundfos Conlift1 LS data (retrieved 21 October 2026)
  7. CoolEasy condensate pump buyer's guide (retrieved 21 October 2026)
  8. condensatepump.co.uk boiler note (retrieved 21 October 2026)