A bit disappointed in Ikea. We've got a kitchen tap with a removable spout. After only 10 years it has worn out. Ikea dont do spares. It also seems that they build stuff using bits they found lying around. The hose needs to be M15 x 1 female to 1/2" female. I only worked this out after a lot of research. I can find shower hoses like this with a smooth outside, but nothing with the normal corrugated hose. A smooth hose would jam in the neck of the tap. And it's made by Grohe, so the price is stupid (40€ + delivery)
A replacement tap from Ikea is nearly 200€, so 40€ might be fair, but it's not sold as a spare for Ikea so it might not fit.
A french forum has 2 people trying to find the same part.
https://www.forumconstruire.com/construire/topic-344258-difference-15x100-3-8-flexible.php
https://www.forumconstruire.com/construire/topic-344392-denomination-raccord-femelle-15mm.php
tldr;
Short version is they bought a M15x1 male to 1/2" female and found a coupler in the heating section. I can find a coupler, but it's 10€ plus 7€ delivery. They ain't very common.
I guess everyone else just bins the tap and gets a new one.
I ended up taking the female union off the old hose and soldering it to male on the mixer. Sounds harder than it was. I can now swap the hose easily in the future as M15 x 1 male to 1/2" female are readily available. Fancy that. Spares that can be bought off the shelf. A male end passes through the spout a whole lot easier than a female. Trainee's first job at Ikea?
I'm guessing the ceramic mixer will fail tomorrow. And that will be the end of the tap. If Ikea build custom stuff (that the customers pay for) instead of looking at the market, I can't imagine that the mixer cartridge will available. It'll be 1mm off.
I should have bought a 3/8 to 1/2" hose as 3/8 should pass, then the adapter would have been easier. I have a feeling they are just as common.
The soldered join is at the tip of the blue screwdriver.
