I have just had a bit of work done at home on the wetback (leaky feed pipe).
The HWC (hotwater cylinder) needed to be drained as you'd expect. it is fed by a header tank.
The issue is now that the hot water is barely flowing in the bathroom (vanity, bath, shower). The kitchen/laundry is fine.
Under the house there's the mess of piping with two red twisty turn valves.(top one is #1 and bottom is #2)
#1 valve will disable hot water for the entire house (trial and error) the other valve #2 resumes hot water in the bathroom, but I'm pretty sure the header tank stops filling in this configuration.
I called the company for thoughts, and got some after hours free advice (vs onsite visit which is super pricey). The advice was that this is probably an air block and we did the finger over the double mixer to push cold water up through the hot pipe to push the air out. We didn't have any luck with this (we heard some gurgles in the pipes but all that happens is the cold that was forced up the hot pipe comes out and we get about 5-6 seconds of actual hot water (good flow) before returning to a trickle/nothing.
I thought i had solved it when I turned on valve number two, but the header tank not refilling made me turn it back off. The header tanks kicks in pretty fast when you run the hot tap.
There is a tempering valve between the taps that get hot water and those that don't.
Any thoughts? :P I'll be getting someone around on Monday, but that means flannel baths until then (grr)