wendydildo

When I was younger (Early 1980s) my dad had a collection of films, they still delight me to this day and I have tracked all but one of them. I think my mum made him get rid of it, because of the content, I am one of two daughters they had...
I watched it a few times before it disappeared from his collection.

it would 70s i guess and american in origin.

it opened on the outside of a wooden house, the first scene involved dad coming into the bathroom and one of his daughters was naked on the toilet and the other was naked in the bath.
He makes a big fuss about of how they have both grown. Eventually there is a bit of mild water sport. I especially remember him peeing on the daughter who was sat on the toilet..
then sex followed.

that is all i remember any ideas?

I would really like to track it down