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Green Building Bible, Fourth Edition
Green Building Bible, fourth edition (both books)
These two books are the perfect starting place to help you get to grips with one of the most vitally important aspects of our society - our homes and living environment.

PLEASE NOTE: A download link for Volume 1 will be sent to you by email and Volume 2 will be sent to you by post as a book.

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    • CommentAuthorandyman99
    • CommentTimeMar 19th 2019 edited
    Is it OK/sensible to supply a TMV with indirect/pumped hot water and direct mains pressured cold water?

    I currently have the hot water pumped with one of these inline devices, recently mentioned on a different thread here:


    I now want to fit a shower in an ensuite. Space is tight so fitting a convention pump would be challenging which is why I’m wondering if I could supply the cold side of the TMV with mains pressured water.

    Are there any regulations preventing this, my research suggests not and that this is simply a “mixed” system.

    Will the TMV be OK with the supplies at different pressures?

    My thinking is that I don’t want to buy a 2nd inline pump for the cold water if the above would work.

    Water supply is reliable here and there will be alternatives using stored water if the supply did fail, so isn’t a major concern.
    • CommentTimeMar 19th 2019 edited
    Did you look at https://www.showerpowerbooster.co.uk/information/improving-pressure-flow-taps-showers-gravity-hot-mains-cold-systems/ ?

    edit: personally I'd probably look at reducing the mains pressure to the shower rather than adding a second pump.
    I have to say I'm surprised by the whole idea. I would have thought a hot+cold pump was a better idea.
    • CommentAuthorandyman99
    • CommentTimeMar 19th 2019
    Yes, but I can't find any other corroborating information. I'm not sure I would really expect it to work since the hot water will be at a pretty low pressure (bungalow with a couple of meter head only) and the pump helps but isn't exactly dramatic compared to a conventional shower pump.
    • CommentAuthortony
    • CommentTimeMar 19th 2019
    There are some shower valves that can cope with mains pressure cold and low pressure (3m+ head) or pumped hot
    I fitted a venturii shower in the old bungalow which lasted ten years and was still working when the bungalow was demolished. It used mains pressure cold and vented tank hot supplies. A lot easier and less noisy than fitting pumps.
    • CommentAuthorCWatters
    • CommentTimeMar 20th 2019
    What condition is your hot tank? Would it make sense to replace it now with a mains pressure tank/megaflow?
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