Looking for some advice, every time it rains my rear passenger footwell floods really badly. Took approx 6 litres of water out yesterday.

Can’t seem to find the source and wandered if there are any areas that are prone to leaks?

The water seems to appear from nowhere, the door seals, window seals, A/B/C pillars, boot, front footwells and roof linings are all bone dry. Even the footwell above the ankle level are dry, indicating water isn’t coming from the door area. The water gets in even with the car being stationary. 

The only two things I can think of are the sunroof drains (as I believe they expel water in the region of the rear footwells) or the aerial (but would assume both footwells would have some water in, not just the passenger side) any pointers would be much appreciated as it seems to be getting gradually worse. TIA. 

Edited August 22, 2025Aug 22 by CJT94

Morning Chris 

Welcome to the Forum

That's a lot of water 😢 I fixed a 5 series for a friend of our son his was no where near that bad though.

With the 5 series the rear door card had been removed at sometime and the vapour barrier was missing that added to the drains in the bottom of the door being blocked. The bottom of the door was just full of water. When it rained or he went through a car wash it overflowed and filled the footwell. I cleared the door drains a lot of water was held in there I dried it out with a heat gun (checked the roof drains as well they were OK) Fitted a new vapour barrier took out the carpet and sound deadening thick pad which was sopping, gave them a spin in the washing machine then dried in the sun. While they dried I jet washed the car to check for leaks (none found) so I replaced the Door Card sound deadening and carpet he has had no issue over the last 3 years.

With luck that will be your problem 😁 If it isn't then you have a serious leak under the car or in a seam

Hope this helps not hinders

Dave

ah, obviously the foot spa optional extra wasn't installed correctly.

Did you find the cause?

Water is a sod, I had a slight leak into my wheel well (about an egg cup full).  Tried it out and kept an eye on it, it never has so far come back and I never did find the cause.  My current working theroy is that it may have been when BMW wet vacced the carpet before sale.

I know it sound rather rudimentary but you could try taping paper towel around the footwell above the waterline, that would at least give you an idea of where it's coming from if it's coming from the sides.  

If its holding that much water then I would'nt have thought it would be leaking from underneath as surely it would drain away.  Is the carpet in the front dry?  Door seal on correctly?  My old golf, I had slightly moved the door seal and it was suprising how much water did get through.  Do you have any drain holes somewhere near the boot hinge?