Drinking from the Tub is it Safe?

[kitty kisser]

My cat is 3 years old and female. I provide unlimited access to water with a 1/2 gallon water dispenser. The faucet in the bathroom drips and my other cat a calico will only drink from it. Rose my long haired black and white cat likes to jump in the garden bath tub and drink the residual bath water. I'm worried cause it has soap and shampoo in it. Does anyone know if it is harmful?
After I clean it weekly I try to keep the door closed until it's been rinsed well and used at least once. Rose watches me take my bath and occasionally drinks from the tub while I'm in it. Don't know how to break the habit she meows at the door if I don't let her in. The bathroom is her favorite room cause the pigeons peck at the sky light. Any ideas of how to break this habit or is it ok?

 

[misstufts]

I've had this same issue with my cats. I'd be worried about the soap being toxic.
I would thoroughly rinse your shower/tub after each use. But what I've done to sort of deter them from drinking elsewhere is add more fun drinking areas. I have a turtle tank that's now on the floor, it has treated safe water in it and they enjoy that. I placed a water fountain in my bathroom to give them that same effect of drinking running water. I have several fountains around the house to let them choose safe areas for them.
I would suggest trying to keep the door closed in the bathroom, and place more interesting water areas around the house. Some cats just like a little fun when it comes to drinking!