How to unblock bath

[IncessantNameChanger]

The water was draining slowly in the bath and I presumed it was clogged with hair. I have tried drain snakes but they never go around the u bend. Dh put some power cleaner in the plug hole and lots of black Mouldy scummy water came out. So it looks like a build up of soap scum in the pipes. Now there is a pool in the bath. Any ideas of what to try next?

Plunger?
Can you get to the ubend if you take off the side panel, unscrew it & see if it's blocked?

I used to get a weird black slimy build up that narrowed the pipes & had to de-slime the u-bend periodically.

When had this I closed all other holes with plugs or bowls over the shower drain and plunged it. It worked and cleared the blockage

Plungʻer seems to work for a bit but a week later it's the same again. It's a old fashion pedestal sink so tight to get your hand the back to unscrew. Dhs arms don't fit. I can't seem to un screw it

I'd try again with the chemical cleaner.

We had a sink that used to drain very slowly and block frequently. When we finally took the U-bend apart we found one of the kids had stuck a pencil down inside it causing other muck to stick and build up quickly.

Caustic soda maybe? I find it good for stubborn blockages.

Try the drain opener again. Make sure you leave it in for the maximum time.

plug up the overflow hole then use a plunger with force

When our shower wouldn’t clear with drain snakes or heavy duty chemicals we used the jet washer and blasted it down the drain hole.
I think this is risky in case it moves a solid object further down the pipes or cracks a pipe but we were luckily ok.

I'd probably try caustic soda first.

You could also try wearing a rubber washing up glove while you try to undo the pipe. If that doesn't work, can you get a pipe wrench? That would give you a lot more leverage to undo the u-bend. You do have to be super careful if you've used caustic soda/other cleaners though as they won't have gone if the drain isn't draining.

https://www.goodhousekeeping.com/home/cleaning/a69800134/how-to-unclog-shower-drain-fast/ - I used this for the first time yesterday on my shower - worked a treat !

How to Unclog a Bathtub Drain: 11 DIY Clog-Busters - you have tried these

I'd carefully remove the bath u-bend. Search for a video for instructions.

The gunk will probably be slimy from soap and conditioner.