This is a problem that has been bugging me intermittently for a couple of years. Condensation from evaporator doesn't flow properly down the A/C drain so water can drip or pour into the cabin. I have been under the car I cleared the drain from below & also removed the panel under glove compartment & left side panel to clear the drain from above.

I think that the rubber drain itself is perished & has a small split that allows water out when it's very humid & there is lots of condensation from the evaporator. I haven't been able to find the correct part number or even a good diagram or photo showing the drain itself. There is a drip tray under the evaporator that has a spigot either side that the drain plugs into. Unfortunately it looks to me as though it's a dash out job to replace the drain & I suspect that these are NLA new.

I think that the alternative solution might be to replace the drain with a piece of plastic tube. It might even be possible to run the tube within the drain without removing it. I welcome any other suggestions

I'll be replacing my AC evaporator this weekend so the dash will be coming out. That will give me a chance to see the anatomy of what is in there and hopefully work out where the leak comes from. When I took the red one in for MoT, water was dripping at a pretty good rate out of the drains yet when we used it last weekend, there was still water dripping onto the passenger carpet inside as well, so I think that one must be partially blocked.

Generally just the side panels off to access the corrogated pipe, but it easier with HEVAC controller out. That way you can get two hands on them.

Mine often fell off, so I put them in a cup of hot water for 15 mins & then stretched them a bit before re-fitting. Much better now & the puddles are under the car as they should be.

If you are talking about the fat ones either side of the HEVAC, they feed heater output to the vents under the front seats. The AC evaporator drains are much closer to the bulkhead and are about 1/2" diameter.

But to Nigel's problem. The evaporator sits in a plastic box with a gutter along the bottom and the two stubs that go onto the drain tubes.

This is the two tubes sticking up from through the floor

Now the gutter is going to sit horizontally so why is it always the passenger (driver's side for those with the steering wheel on the wrong side) that dribbles into the footwell? In my case it was because the drivers side drain tube was blocked solid so all of the condensation would have to go out the other side. On a humid day, there's a lot of condensation to drain and I suspect the one tube simply isn't big enough. If it can't drain away it fills the gutter until it overflows into the duct from the blower. If you look at this picture you can just see a tidemark where the water level has got up to.

It looks like water has even got up to the join in the casing at some point. As the foam in the joints of the ducts rotted away years ago, they don't seal so what water can't get out of the drain will run into the duct and dribble out of the joint onto your passengers feet. Icy cold water dripping on their tootsies isn't going to go down well (as Nigel has found out).

Now we know the cause, how can it be sorted without going to the lengths I've had to go to today? First step would be to clean out the drivers side drain tube as I suspect it will be as clogged as mine was. I suppose it would be possible to put a small hose up through the driver's side drain and dribble some water slowly (enough to flush the gutter but not to fill the duct) through to flush any debris that may be blocking it out through the passenger side drain. The duct from the blower on the driver's side is higher up so that one won't fill up with water.

Having done mine and had it re-gassed so the AC is now working perfectly, I suspect I have found the reason for the water dripping onto the passengers feet. I've just taken my car in for MoT and while it was on the ramp, water was dripping from the AC drains. But NOT from the passenger side but from the drivers side. I didn't notice if the bottom of the evaporator housing was sloped or not but my driver's side drain was clogged solid. I suspect if that is clogged, all the condensate has to get out of the passenger side and it can't get out fast enough. So while the passenger side drain may be clear, if the driver's side is clogged, the passenger one can't cope with the quantity it has to drain.