About 3 weeks if I remember correctly, but I did check with my GP first. He was very good about doing my first dressings at about 10 days, and then a week later took dressing off completely, thats when I said to him I would like to get back in the pool, to start exercising, he said no the first time I asked, and told me to come back in a week again, thats when he gave me permission.
He did examine my cuts very carefully, to make sure they had healed completely, he said wasn't worth the risk of infection to go in too early.
Only comment I would make is go in early, before the kids get there, just a little quieter, you don't want some kid to hit you even accidently.
I also took my walking stick with me as a warning device, to others that there might be something wrong with me even after I didn't really need it, expecailly when going shopping/supermarketing, you can use it as a crash barrier for little kids, rather than your leg, couple of times stopped a very painful experience.
I started my pool experience after THR, just doing my post surgery exercises very gently, using the weight of the water as extra effort, and then getting a noodle under my arms, floating and just bycling in the water, still do it a year later, then some more stretches, and out, 20 minuetes probably enough the first few times, now I do over and hour 3 times a week.
Just had another check up with the physio, she was delighted just how strong I was, and she was able to demonstrate to me how strong I was, which has given me alot of confidence, which had taken a knocking due to my left hip being not so good.