Can I use an HD extension lead to my shed?

Hey hope your well I would recommend running a 2.5mm SWA Cable from your outside socket and installing a double socket and switched fused spur in your shed to feed your fountain, hope that helps Thankyou

there is no regulation to say you can't do this but you need to take in consideration of what you have on your ring main at the moment. my advise would be run a new circuit from your consumer unit in the house, to the shed using a 6mm sea cable. fit a small consumer unit to run your electrics in the garden and in the shed. that way if there is a problem it won't take out the electrics in the house.

There are regulations for this but the are related to PAT testing, extensions leads are only meant to be used as a temporary measure, not for permanent use, the items you are attaching would be permanent and would need a supply as part of the fixed installation.

In this instance I would mount a switched fused spur next to the existing outside socket and incorporate both onto the house ring final circuit. From here I would take a swa 2.5mm 3 core to a 2 way garage DB. From here feed your pond pump, fridge freezer and shed lighting. Depending on the earthing arrangement at your property an earth rod may need to be installed. Also this work is notifiable and would require an electrical installation certificate.