Re: creda simplicity. washer, w100fw
Adv, even if you don’t have a megger, (we know you use a PAT tester) an ordinary multimeter will usually show up low insulation faults on the Megohm scale, though not always.
Or, as Penguin says, just disconnect and try.
And heaters rarely give trouble in soft water areas. It’s the scale that kills ’em.
Mike.