I want to use an old washing machine that is in our barn for washing all the
dirty horse/dog towels and other dirty stuff. We have electricity in the
barn, but no plumbing.

Would it be possible to rig up some sort of system like having 2 black
dustbins either side of it - one for clean water and one for discharged
water? Does the machine suck in water or does it need to be pressurised?
Any ideas what sort of pressure (if required) - I have a 1000 litre IBC
outside the barn which can produce a fair bit of pressure when full - would
I be better using that as the supply? Can I use rainwater for washing (it's
breaking the machine I'm worried about - not the cleanliness of the rinse)?

What about the discharge - can I put that into the ditch? We have a septic
tank system, so not sure if our surface water goes into that, or straight
into the ditch. Or should I put it down an internal "dirty water" drain?

Many thanks for any comments!