can I remove cold water tank post CH install?

Probably not - unless you want it for some reason (like if you have a unreliable supply)...

There is a slight risk that the toilet cistern valve may not handle the pressure rise (pretty unlikely)... you can assume the bath and basin taps will be Ok since they are coping with mains pressure on the hot one presumes.

No, am in the middle of London with a good supply. I in this small flat I could really do with the room the tank takes up.

OK, thanks. So I should be standing by the toilet cistern when I've put mains pressure to it then, ready to turn the stopcock!

Thanks, John, for your help.

I should not worry too much (well at all in fact)... if it is not happy is is more likely to make itself known by banging excessively on shutoff, or by continuing to drip and causing the cistern to overflow. The chances of it having any difficulty really are very small though - I only mentioned it for completeness.

Just a note about an occurance here on Sunday last. The house was built with a HW tank, but converted to a Combi-boilered mains pressure system in the early 90's. Sometime, possibly later, I don't know when, a new plastic toilet cistern (Fordham FlushPanel) was also fitted. I also have hostital-style taps with 90 degree levers. I shut the cold tap on the sink rather sharply, and heard the plastic diaphram valve in the cistern explode! Well, in fact, one of the plastic parts inside had been overtightened and the increased stress from the water hammer made it split - our water pressure here is high, so a fountain of water from the cistern resulted - fortunately the main stopcock was within reach and only about a gallon of water overflowed. It's made me look at brass ball valves with a whole new appreciation!

The moral of this story? You might have to wait a bit to be sure that the mains pressure isn't going to result in a leak. However, I think my experience is unusual.

R.