Pipe sizes for shower pump into bath mixer

17 Aug 2009
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United Kingdom
I have a varispeed50 installed underneath my hot water cylinder. The hot supply comes out of the side of the cylinder about 3/4 of the way up using a 15mm pipe. The cold water also using a 15mm pipe comes directly from the storage tank in the loft. Currently the pump feeds a shower mixer all connected with 15mm pipe.
I recently installed a bath mixer tap with a shower attatchement which is fed with 22mm pipe. But it looks like I have the same problem as other threads I have read, where the tap is for a high pressure system and not gravity fed, as the flow out of the tap is quite slow.
The idea I have is to use the shower pump to feed the bath mixer and remove the shower mixer.
But, the bath mixer has 22mm fittings and the pump 15mm. If I run 15mm pipe to within around 300mm from the bath mixer then get a coupling to attach to the 22mm pipe, will this work alright or will there be a pressure drop. (the bore size reduces again inside the mixer tap)
Any suggestions?.
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