Unless you are using organic, environmentally friendly and biodegradable products like Ecover it really isn't advisable, you will be polluting the soil, it is not a good idea to put into your pond either. Realistically you are not going to get an awful lot of water from your tumble drier in any case - did you mean washing machine?

Take a look at this site for info:
http://www.goselfsufficient.co.uk/using-grey-water-in-your-home.html

The chemicals are not a good idea in a pond full stop, and if you have pond fish this and tap water is harmful to them. You can buy 'Pondsafe to treat the water as you add it to the pond but dont think its meant for washing machine water.

Thought as much!! that's why I have'nt done it before!! And yes i did mean tumble dryer as the excess water goes into a little tank which needs emptying every so often! But thanks for your comments x