"John Stumbles" wrote in message
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On Thu, 26 Jan 2006 18:58:57 +0000, John Stumbles wrote:



SMIP

Thanks for all so far. Thinking about it, there is a mixer tap in the
basement kitchen but I can't see mains water pushing back the HW against
the head it has down there. I can't remember if the bath on the ground
floor has a mixer but it's certainly not a bath/shower mixer. The shower
itself is pumped off the storage tank.


If the MCWS head is adequate to push up to the storage tank above its enough
to create your problem John
Have you tried turning off the cold supply and seeing if it continues to
present the problem?
The flow from the vent pipe is a continuous slow run - not a trickle but
not a gush, certainly not full-bore.

I'm wondering whether I've got my calculations right: anyone like to look
them over?