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Drain blaster buying guide

Updated: 23 October 2026

You are at a slow kitchen sink in a UK flat, and every amazon.co.uk title says unblocker. This drain blaster buying guide is the decision before the price table: whether you need a force pump, a stored-air gun, or a dual-cup plunger, and whether the cup will cover the hole. A star rating cannot cross those types. Prices are GBP from the saved amazon.co.uk listings, captured on 21 October 2026, not a live scrape. The Products Compared editorial team did not run a lab test. A qualifying purchase can earn a commission at no extra cost to you. The rows are on the [drain blaster comparison](/hub/diy-supplies/drain-blaster).

You are at a slow kitchen sink in a UK flat, and every amazon.co.uk title says unblocker.

Our top picks

Rothenberger Rothenberger RoPump 71991

Best overall

Rothenberger Rothenberger RoPump 71991
8.6/10about £21.92
View offer
HzNzYHD HzNzYHD air drain pump, four suckers

Alternative

HzNzYHD HzNzYHD air drain pump, four suckers
8.4/10about £14.99
View offer
XREXS XREXS drain buster, two cups

Best value

XREXS XREXS drain buster, two cups
8.0/10about £12.34
View offer
On this page
  1. 1.Three tools, one search result
  2. 2.Match the cup to the hole
  3. 3.Read the pressure line before you trust it
  4. 4.What this guide will not pick

Three tools, one search result

A stored-air drain blaster, as Wonkee Donkee describes one, is a cylinder, a non-return valve, and a trigger. You pump, seat a rubber adaptor, and release one shot. The blue ABS guns in this set sit mostly around £9 to £15. The Rothenberger RoPump 71991, at about £21.92, is a suction-pressure hand pump. The listing names sinks, urinals, showers, and bathtubs, states 50 psi and CE, and does not list a WC. Super Plus, article 072070X, has a long WC adaptor and is not in this set. The XREXS, at about £12.34, uses a 15 cm cup or a 6.3 cm cup and has no trigger. A 4.0 from 3,987 reviews does not make it a gun. Saved prices run about £8.99 to £12.34, about £14.99, and about £21.92 to £22.99. Huws Gray listed 71991 at £35.51 including VAT.

Match the cup to the hole

England's Approved Document H gives minimum traps: a washbasin 32 mm, a bath, shower, and sink 40 mm, and a WC outlet 75 mm or 100 mm. That is building guidance, not a tool certificate. Scotland and Northern Ireland use their own rules. The useful point is the hole in front of you. A large WC cup will not seal a shower tray. A reviewer put the RoPump bell at about 95 mm and missed a recessed kitchen waste. Stated ends run from about 1.5 cm on the LSDZHK to about 20.5 cm on the Lichll. The XREXS splits 15 cm for a toilet and 6.3 cm for a sink or bath. The YWHWLX prints four suckers and no diameter. If the rubber rocks, the shot becomes splash.
Rothenberger Rothenberger RoPump 71991

Testsieger

Rothenberger Rothenberger RoPump 71991
8.6/10about £21.92
View offer

Read the pressure line before you trust it

The RoPump listing states a maximum of 50 psi. Do not copy a 4 bar figure from a different Rothenberger cleaner onto 71991. The inShareplus kit, at about £22.99, prints 8 bar (8 PSI) beside bands of 2 to 3 bar, 4 to 6 bar, and 7 to 8 bar. Eight bar is not 8 psi. A gauge does not repair that mix. Leave the kit off a shortlist if you need a number you can quote. HzNzYHD and XMPEKO both say about 12 times atmospheric pressure, with no test in the saved listings. Wonkee Donkee uses about 3 to 8 pumps, fewer on delicate pipework. Silverline, for a gun that is not an ASIN here, says four pumps on plastic. A bullet of 10 to 20 strokes is that listing's instruction. The JJX at about £8.99 is cheap, and most printed reviews in that saved listing are not marked United Kingdom.

What this guide will not pick

The named top pick and the best value live on the best drain blaster page. This guide stops at the mechanism and the cup. Price and stars for all ten stay on the main comparison. A square pan belongs on the toilet page. If a corrosive cleaner is already in the pipe, do not buy a gun to fire into it. Push-fit plastic wants a modest first charge. A UK review of the JJX says a high first release can force joints apart. If the card is missing, do not invent a higher count from another brand. Electric guns and Monument cups appear in UK search and are not in this set.

Common questions

Is a drain blaster the same as a plunger?
A stored-air blaster holds a charge and releases it with a trigger. A cup plunger, including the XREXS, is stroked and has no trigger. The RoPump 71991 is a third tool: a suction-pressure hand pump for sinks, showers, and baths. Amazon files them together under unblocker. The mechanism on the listing is what you are buying.
How do I match a cup to a UK waste?
Look at the hole, then the stated cup. English drainage guidance uses a 32 mm washbasin trap and a 40 mm trap for a bath, shower, or sink, with a WC outlet at 75 mm or 100 mm. A 20.5 cm Lichll sucker is a large end. A 1.5 cm LSDZHK adaptor is a small one. If the rubber does not sit flat, change the cup before you add pumps.
Why does one listing say 8 bar and 8 psi?
The inShareplus page prints 8 bar (8 PSI) and bar bands elsewhere. Those units are not equal, so the bracket is not a conversion you should repeat. The RoPump 50 psi line is a single unit. Leave the inShareplus figure as printed.
Does about 12 times atmospheric pressure mean I should pump to that?
That phrase is a bullet on the HzNzYHD and XMPEKO listings, and neither saved listing contains a test. Their pump counts are instructions, not a measured pressure. On plastic waste, keep the first charge to a few strokes past resistance. Follow the card in your box.
What should I skip if the pipe under the sink is push-fit plastic?
Skip a first charge at the top of the listing's pump count. A high shot can disturb a push-fit joint, which a UK review of the JJX reports. You still need a cup that seals. If the joint is already loose, or more than one fitting is slow, stop and get a plumber rather than adding strokes.

Related pages

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Best drain blaster for a slow UK sink, bath or shower

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Sources

Public UK sources and the amazon.co.uk listings compared on this page. Listings captured 21 October 2026. Updated 22.10.2026.

  1. Wonkee Donkee: how a power plunger works (retrieved 22.10.2026)
  2. Silverline drain blaster manual (retrieved 22.10.2026)
  3. Approved Document H, drainage and waste disposal (retrieved 22.10.2026)
  4. Thames Water: blockages (retrieved 22.10.2026)
  5. GOV.UK: sodium hydroxide (retrieved 22.10.2026)
  6. NHS Wales: safe use of liquid drain cleaners (retrieved 22.10.2026)
  7. Citizens Advice: who repairs drains and sewers (retrieved 22.10.2026)
  8. Consumer Rights Act 2015, section 22 (retrieved 22.10.2026)