@somerpark 

My reply regarding retention wasn't addressed to you.

@ianmk13 

Go ahead then.

Posted by: @ianmk13

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@morgan  Why not?  There’s hydraulic separation between the ASHP flow and the domestic hot water

Coil probably not large enough, although this can be overcome by 'plate loading' ie fitting a phe and pump to replace or supplement the coil.

I debated retaining my vented cylinder but was persuaded to change it for a uvc (by an installer who was quite happy to fit a supplementary phe if I wanted him to).  For me definitely the right decision, no pumps anywhere, balanced, potable hot and cold everywhere, better water flow.  I replaced my pumped shower with a very smart but simple, non thermostatic, mixer (Grohe, about 60 pounds).  The only downside is that the airing cupboard is now barely luke warm because the insulation on the new cylinder is so good, even though I instructed the installer to omit the insulation on the adjoining pipework.  Of course this decision is very circumstance dependent.

@morgan sorry my mistake

@somerpark no worries.

@jamespa I'm not suggesting retaining an existing cyclinder.  Replacing with a new cylinder, but venting is preferable to adding a PHE and extra pump, I believe.  I have two reasonably new (and expensive) digital showers. I have a poor mains supply to my home (lawn sprinkler only covers approximately 1m radius). There would be no advantage to spending extra money on replacement shower units and having poorer showers as a result.

Posted by: @ianmk13

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@jamespa I'm not suggesting retaining an existing cyclinder.  Replacing with a new cylinder, but venting is preferable to adding a PHE and extra pump, I believe.  I have two reasonably new (and expensive) digital showers. I have a poor mains supply to my home (lawn sprinkler only covers approximately 1m radius). There would be no advantage to spending extra money on replacement shower units and having poorer showers as a result.

Fair enough.  With poor mains pressure the only advantage of a UVC is that it is sealed and so less likely to get general detritus in.

@jamespa Install one of these on the main incommer.

Thanks, its actually @ianmk13 that has the need so tagging him so he sees your post

@jamespa Thanks. Yes; I'd seen it.  To be honest, it's an option I had not considered as I was under the impression that fitting of a pump to the incoming main was not permitted.  Apparently it is if the flow is limited to 12L/min. In my case, however, my prime motivation is to not have to replace the 2 nearly new and expensive shower units.  That's a cost I can easily avoid.

It would be nice to fit a pump to my garden sprinkler in summer but I suspect it would simply draw air in from the water tank feed or the kitchen tap when used.

@ianmk13 

I had to do that for my garden sprinkler at a house I once lived in.  Got around it via a Fred Karno method by using a large water butt with a submersible pump within attached to the hose to the sprinkler.  A hose from the garden tap running constantly into the water butt. Bit of a faff but it certainly upped the water pressure to the sprinkler.

@morgan Oh! A Buffer Tank! 😉 Toodles.