Installing new vented hot water cylinder direct combination unit

[blakey]

On Easter morning my partner and I noticed our hot water had turned cold. We have a vented hot water cylinder 900x450 direct combination unit with immersion heater bottom left side and separate open top for cold water, which is transferred to base of tank. The immersion heater was not working so we decided to change the whole tank as the one we had was in a state and we could not budge the immersion heater element. The new tank is exactly the same except on the right side where there is two holes, one at top of lower tank [hot water outlet] and one at base drain valve.
The hot water outlet is about an inch or so higher on the new tank so we have had to obtain a flexi-extention. Everything we have managed to transfer accordingly, although have had a few leeks through not tightening nuts sufficiently. We were told that PTFE tape would be sufficient but have now used hessian fiber as well which has done the trick. Unfortunately, a leek also sprang around back as there are two other holes which could be used to set up tank on left side, these we had to seal with flow stoppers but have also needed hessian which I am tackling today. The whole tank is in a small cupboard, very awkward so need to get everything right. Yesterday before we noticed leek at back, we filled tank up. We have ball cock at top which stops water flow when filled. Placed the immersion heater on and after about 20 minutes my partner tried the hot tap in kitchen but nothing came out. Immersion working fine. Our neighbour, who is not a plumber, suggested we give it time to fully heat up as heat rises and in turn pushes water out of hot water outlet. We took our neighbours advise and allowed the water to further heat for about an hour. This time there was dribbling from tap including taps in bathroom, although a little more coming out of bathroom tap then from kitchen tap. We were wondering if new flexi-connection was the cause it has a shut off valve, although this is open for the water to flow. Also, as this has not been changed in 40 years, could there be air in pipes?
Because of leek at back, we have had to drain tank so all areas can be completely sealed. As mentioned above the only real problem we find is receiving hot water from water outlet. Any good advice welcome.

Why did'nt you call a plumber to do your job,all you have done is created problems for yourselve's.
Have you not read the papers about incorrectly fitted hot water cylinders killing people.
Rod Hull of emu fame did the same trying to save a few quid by adjusting his tv ariel,he fell and died.
so please leave jobs like plumbing to real plumbers.

Sounds like air !Do you have a mixer tap on your sink or bath? If so try holding your hand over the outlet of the tap and turn on both hot and cold to force the cold mains through the hot pipes this will expel any air. if you dont have a mixer try using a piece of hose and two tap connectors between the hot and cold taps.
Hope this helps.