with 5 girls, i use the washable pads that are used in the hospitals. I bought them on ebay. They are big and have the waterproof bottoms and soft cloth on top. They can be cremated in the wash every week and they still work. I know some lose their waterproofness if they don't use a good PUL fabric. That is the waterproof fabric that is needed.
If you pull up washable pee pads on ebay you will get a ton of the washable ones. I think i got 12 for $25. They are heavy duty and I have had mine for about 3 years now and have had no issues with them leaking.
Highly recommend the washable to the disposable.
Here's an example of the ones i have:
They are 15 for $19 + $18 s/h but that is still cheap for 15. These pads weigh 1.5 lbs. each so that box will be heavy!
15 Washable Puppy Pads Pooch Incontinence Pee Wee Dog - eBay (item 400178075608 end time Jan-01-11 22:11:23 PST)