I've searched and read many tips and quite a few questions on here but I'm still totally stumped!

I have a bathroom single lever mixer tap, and I'm 90% sure the cartridge needs replacing so thought I'd give it a go as it seemed pretty straight forward. I removed the handle of the tap, no problem, but the decorative bonnet (I've seen it referred to as a bonnet and a sheath) is not budging!!!

I have tried white vinegar to remove limescale, I've tried oust to remove limescale, I've tried WD40 to lubricate, I've tried a strap wrench but can't get a good grip because of the angle of the bonnet, I've tried heating it up with a hairdryer, I've tried pouring some boiling water over and using rubber gloves to twist it. Nothing is working. I've left oust most of the day and separately left WD40 overnight and neither seems to have helped...

A decent amount of gunk must have been dissolved as before the liquid would just sit at the top and it now oozes through suggesting it's working it's way through the thread?

Please any tips, advice, anything would be greatly appreciated! I'm not sure I've tried the "heating" methods enough to get it hot enough but I don't know how hot it needs to be?

Calling a plumber is an absolute absolute last resort and any way I don't have to would be preferable!

Many thanks!

Pictures of tap for referencepicture of tap

picture of tap from above

  • Have you tried grabbing it at the base with some Channelocks and turning it? Not my first choice but beats paying a plumber.
    – JACK
    Oct 13, 2020 at 22:32
  • Welcome to Stack Exchange! You should take our tour so you know how this site functions. If you have a brand name for the faucet it might help. I'm wondering if that chrome bonnet even needs to come off to remove the cartridge. Hard to tell from the pic but are there notches in the top rim of the brass inner ring that might enable you to unscrew the cartridge? Just a thought.
    – HoneyDo
    Oct 13, 2020 at 22:34
  • The faucet is an NK Porcelanosa and I watched a YouTube video of a very similar Porcelanosa tap where the bonnet just unscrewed. There aren't any notches on the brass ring unfortunately, and generally nothing to get purchase on inside.
    – GiveItATry
    Oct 14, 2020 at 6:56
  • @JACK do you mean turning the square base of the faucet and holding the bonnet? Or using channelocks to try twisting the bonnet?
    – GiveItATry
    Oct 14, 2020 at 6:58
  • @GiveItATry Channelocks to try twisting the bonnet.
    – JACK
    Oct 14, 2020 at 11:42

2 Answers 2


You might try loosening the adjustment ring, the brass ring with two slots for a spanner wrench that's inside the bonnet of many single-handle faucets.

Adjustment ring spanner

Those spanners often come with faucet repair kits, along with springs, O-rings and other parts, but could be easily fabricated with some heavy-gauge sheet metal and two bolts with nuts; file the end of the bolts to fit the slots.

That said, the adjustment ring could be frozen as badly as the bonnet. Recently, I had to replace a similar faucet; the bonnet was stuck so tightly that on turning it with a large strap wrench, a rusted bolt holding the faucet to the sink broke! In that case, it was not a loss, because I had planned already on replacing the ancient faucet.

  • The brass ring inside is smooth on top with no notches, so I don't think it is an adjustment ring. It looks like the top of the knot underneath the bonnet that holds the cartridge in place.
    – GiveItATry
    Oct 14, 2020 at 7:00
  • This was one of the videos I watched before even attempting the job, same make and an almost identical tap, and the bonnet just unscrews super happily... the white bits appear to be the top of the cartridge underneath the nut that holds the cartridge in place porcelanosa-usa.com/wp-content/uploads/2017/09/…
    – GiveItATry
    Oct 15, 2020 at 8:10
  • Darn. Good video, and it's obviously a standard right-hand thread on the bonnet, as it's being unscrewed. Perhaps using rubber sheet jar-lid remover or rubber from an inner tube could provide a better grip. Or, last-ditch effort, damaging bonnet: drill two small indentations in the bottom of the bonnet, and use a spanner to fit the pinholes. Oct 15, 2020 at 23:15

Thanks to the suggestion of @JACK I bought a slip joint wrench which worked! I had to use some first aid stretch fabric strapping tape and a cloth over the bonnet to both get a grip of the strangely angled thing and not completely gouge it (tried electrical tape which I read somewhere else and it just slipped straight off) but it finally gave way and I've managed to remove the faulty cartridge!

Thank you @JACK !!!!

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