15kg bucket is definitely worth it when u have 3 horses.
The vet gave my wee rescue pony an ultrasound and found she had a very heavy sand burden. I tried sandflush with 2.5mg of epson salts (as recommended by the vet) and did the 5 day treatment. The vet returned 3 weeks later and redid the ultra sound. The sand burden had reduced by half!! What a result and it was direct prove that the Sand Flush was working. While she has not had an ultrasound since (4 months ago) she is now on the sandflush for the 5 days every month and she is looking happier and healthier.