IMM wrote:
> "Roger Wareham" <rmw29@eng.cam.ac.uk.XX> wrote in message
> news:be0rom$p9p$1@pegasus.csx.cam.ac.uk...
> 
> 
>>I replaced our HW cylinder with the simple directly-heated version about
>>three months ago.
> 
> 
>>The only disadvantage I have found in the direct version is that it more
>>or less doubles the total capacity of the CH system. I've had the
>>overflow running on one occasion, but I think that was because I didn't
>>  drain enough water out before adding the Fernox. Drained out a bit
>>more and it hasn't run since.
> 
> 
> Important!
> Make sure you have enough Fernox in the system.

Thought of a number and doubled it :-) - and then only drained a couple 
of litres to stop the overflow. The boiler is now on all the time, so 
the volume in the boiler circuit should stay fairly constant.

> Does it supply two showers?  How does it perform? Are the shower
> temperatures both controllable?  What size is the cold water mains pipe?

No problems with two showers (but none of us can stand to have the 
shower tap more than half on!). The showers have French thermostatic 
controls (horizontal bar with a tap at one end and temperature control 
at the other) which do a better job of keeping the temperature stable 
than the previous Mira control.

The cold water mains pipe is almost all 15 mm. I expected this to be 
problem but it doesn't seem to be. The drop in pressure from the 
washbasin tap is apparent, but not serious, when the bath tap is turned 
fully on. Which reminds me - all our taps are mixers with aerators on 
the outlet. Without the aerator, the water splashes everywhere!

To be honest, I was prepared to put up with a few pressure problems as 
anything would have been better than the trickle we used to get with 
just a couple of metres head of water feeding the shower, but the 
results have been much better than expected. Our water system is now as 
good as our friends' mains pressure cylinder system.

Roger.