I'm just about to fit another in a brand new, bigger tank. Can't remember off hand, the hole saw is in the shed somewhere, think it's around 63mm but will confirm later this week if you like.
I'll just remove the fittings from my old tank & transfer them over.
Thanks for that, just ordered the element & bits, can you tell me what temperature you recommend, as I have a 650 litre tank ? I am very thankful for all your help
If it's 3kW (as pictured in your link) then it'll raise 650 litres of water by one degree every 15 minutes and six seconds (though that assumes perfect insulation, which, as mentioned above, might not be what you want if you also want the van warm).
So, even if you leave it on from 10pm to 6am, you'll only be raising its temperature by a maximum of around 32deg. It'll be quite a bit less due to heat leakage. Tap water in winter will be around 5 deg C so you shouldn't be able to exceed your target if it's 45 deg. However, plenty of people seem to suggest around 20 deg as a safe limit when it comes to breaking cold windows, so that might make sense.
The other thing to bear in mind is that a 3kW heater will cost around 30p per hour to run.
Vin