Whatever the reason for the dripping security valve…
It sounds to me that you have (in the past) had the thermostat/swich/whatever up too high for safety…
You know that it’s much too hot for more than a second or two on the fingertips… but other folk (Carers) would not expect that situation and they might get scalded.
Just a thought…
Can you explain why Mark? Tastes pure enough to me, from where does it originate?
@Stella It doesn’t immediately come out of the tap scalding, there are a few seconds when it runs cold then through warm to hot, but I take your point. 
Not a problem, I work in the Arts sector and do not judge people.
Just trying to help.
Granted I’m not Mark. From the sound of things it’s the normal water from inside the ballon, forced out through the pressure relief valve - basically just your normal hot water, but possibly sat in a pipe & container for a while, possibly passing across more metal fittings than normal. If you’re happy drinking from the hot water tap than you’ll be fine drinking this, otherwise use it to water plants etc.
Its coming from the bottom of the tank, incoming cold mixed with warm water in the tank. Possibly the right temperature c.37C for any bacteria to multiply (its why the thermostats fir these tanks are set at about 60C). Saying that, its probably perfectly fine to drink, but for the sake of a few litres a day not worth the risk.
OK, we’ll stop drinking it then, but I think, subject to a satisfactory outcome of today’s test at 75% at around 5pm today, I will either leave it at that or return it to the max. Just as it always has been, for at the very least 11 years, when the tank which has just been replaced was fitted.
Thanks to all for the good advice and explanations.
Is the new tank the same wattage as the old one ?.
Water in France is supplied at about 7 Bar where we are so the pressure reducing valve is inside the meter box and drops the pressure to around 3Bar. Unwind the adjustment anti clockwise by 1/4 of a turn to drop the pressure slightly and the dripping would either stop or be less. Adjust again a 1/4 turn until it stops dripping.
No idea Colin, the old one was taken away by the plumber, but in any case, we had the same dripping with that too, it just wasn’t so noticeable because the over flow pipe extended right to the sink.
@Corona I’ll have a look later but it isn’t easy, it is half a metre below gound level in a small box outside.
So is mine 
