[s.hughes]

I need to heat the shed just enough to stop the water freezing and cracking my filter housing.
I could put a mains in the shed but I dont want to. Is there a cheap heater i could use without mains and if so what and where would I get one.
If I do have to use mains then the same question.

Cheers
 

[rg1]

I would get some electricity into the shed then you can use a oil fired radiator. Go for one that is under 1kw  ie 6-800w. It will use about 10p per hour to run and it will keep the frost off.

[michael papworth]

Back in the good old days when I used an RO unit, I used to run it at night. It then couldn't freeze as there was constantly water flowing though it. If I remember correctly, mains water is usually at a temperature of between 13 and 15 deg.

Also. Think about insulation first and foremost. Could you build a cabinet round your unit? If so, you could heat it enough to keep the chill off with a single 100 watt bulb.

[s.hughes]

I have put thick thermal padding around it, the type you put on the old cylinder tanks but even with that it still freezes

[mark dew]

I run an extension lead to the shed to power the booster pump, sub pump, light and a  battery charger. 
Bought this a couple of weeks ago and it works a treat. I have a wooden shed and it raised the temperature from -4 to +15 pretty quickly. It cost somewhere between £1 and £1.50 to run overnight i think.
It has a thermostat and 3 heat settings. I turned the thermostat down to 1/3 of the way on the middle heat setting to keep it around +5 overnight.
http://www.diy.com/diy/jsp/bq/nav.jsp?isSearch=true&fh_search=electric+heater

The 2nd one that cost £19.99.

[AuRavelling79]

Set fire to the shed? It might only work for one night though ....

[s.hughes]

Looks like I will have to run an extension it the shed.
Can I just get any extension lead or does it have to be a certain thickness?

[wezzy32]

i would stick a double rcd socket in shed much safer.and its not that hard todo.

[s.hughes]

I'll do that, but would I need a thick cable to run to the shed i.e does it need to be insulated?

[wezzy32]

mines under ground in the plastic conduit but i did it yrs ago the only prob now is that there is new regs for electrical work at home.