Immersion heater plug socket size

[cjb121]

Hi,
I am just about to fit an immersion heater in an approx 22 yr old cylinder, which does not have one at present.
The plug has a socket nut atop and I wondered what size this might be as I don't have a wide selection of sockets/ ring spanners of that size and don't want to buy the wrong one.
It measures approx 32-33mm or 1 1/4 or 5/16 across the flats... assuming there is a 'standard size'.
Assuming this plug is going to be TIGHT, I don't want to risk an adjustable spanner.

 

[Rob]

Im sure grips (pump pliers) would be ok.

Too much leverage will just rip the cylinder. Be prepared to apply heat and get down the gym the day before!

 

[cjb121]

Thanks Rob,
Yeah OK .. but this nut has nasty slopy sides and not too thick ones either. I can see me down emergency right now

 

[seco services]

cut it out if it just shift. don't waste time on it.