wrote in message
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I use a trevi boost and can recommend them. 22mm hot pipework with
minimum number of bends very important, all the way from HW cylinder
to shower.

If you can't meet the requirements for minimising flow restrictions,
go for pumped.

I once looked into fitting a Trevi - but felt that there were some
uncertainties and significant costs associated with 22mm pipework.

I feel it is a pity that there are no alternatives - perhaps using the cold
pressure to pump the hot - rather than using a venturi arrangement.