good idea cybersye
you can allways pump the ANITFREEZED water back INTO a empty 25 L barrel in the morning, thus you can use it again and again 
are you the guy who i helped set up a RO in a 1st floor flat via the DIY forum ?? ? ?
I had'nt even thought of that ! totally recyclable. Cheers Matt

Dont think it was me although I remember the thread as I look over there ocassionally
I bought neat antifreeeze (2 lrts) from halfords for £10
a 50/50 mix will give you protection down to -34 degrees c, so I've done about 75-80 % water mix thats given me nearly 8 ltrs approx and should see me to -6 ok (south coast).
Pumped through the reel and all hose in the van this evening, doubt I even used 2 ltrs of it (60 meters microbore).
shall keep the 25 ltr barrel in van and just flush it back into that before I connect the tank up again, should last me a long time.