Sparky

I'm old skool as many will agree, switch it on, If it works and nothing blows, its OK that might seem cavalier but, in my day, that was the test,

My first gas job with an old cunt told me, turn the gas on at the meter, note the reading, carry on with the rest of your work, if you smell gas, check the reading on the gas meter, if the needles moved, start looking for a leak, if its ok after about half an hour, its right,

He'd be hung out to dry today but, in the day he was a top plumber,

He uses a mult-function tester. Megger are well known for their MFT kit but they cost £600-£1000 upwards. I bought a no name tester that a few sparks recommended on some forum. It was about £150 I think.

Any 10 quid multimeter can check for continuity (if the resistance is very low between two points, then you have continuity). One of the main things a MFT will do is accurately measure that resistance. Why is that so bloody helpful and part of the testing they do? Consider this. Imagine you've just put in a new ring main with 6 double sockets. EAch ones requires manhandling the cables and eventually forcibly pushing back the socket plate. How do you know you haven't left a lose wire that has escaped its terminal and is just brushing against it ? Your continuity test will show no fault (its still continuous). But its dangerous because you might get sparking between the lose wire and its terminal thus casuing a fire.

The MFT will find that almost by magic ! Basically you test the resistance at several places and if you suddenly get a jump in resistance you know it must be due to a poor connection. I could never explain it all here but you can only do that if you can measure to about 0.02Ohm which means you can measure the difference between say 5M of copper cable and 10M. A terminal screw not fully tightened up would be noticeable.

They also allow you to do insulation resistance testing which means they shoot up to 1000V DC up the cable and check you're not getting any leakage because the inner sheath of a wire has ripped open e.g. because a nail has gone through it.