Shower pump and pumped hot water

Discussion in 'Plumbers' Talk' started by Paul1306, Apr 21, 2020.

  1. Paul1306

    Paul1306 New Member

    I'd be grateful for opinions on best way to proceed.

    I plan to fit twin impeller shower pump to thermostatic mixing shower (via thermostatic bath/shower taps)

    System is gravity fed hot water.
    Mains cold water - pressure fine.
    2 large cold water tanks in loft - base 1m above first floor ceiling, 1300mm above highest outlet.
    Hot water cylinder 1050x400mm on first floor with top feed and Essex flange capped off.

    Current flow to shower/bath is 22mm plastic feed from cold tank solely to cold bath mixer
    22mm feed from HW cylinder to hot bath tap which gives off 15mm supply to downstairs (2 sinks) and individual 15mm supplies to 2 upstairs sinks.

    Flow rate on both hot and cold feeds to highest shower head is 3l/min on both hot and cold

    Initial plan was to keep the existing cold feed, and take the hot feed off the Essex flange capping off the existing hot feed beyond the supplies to the sinks. I was planning to use a 2 bar positive twin impeller pump.

    However a recently fitted thermostatic mixing valve to one of the upstairs sinks isn't working properly presumably because of the hot/cold pressure differential, so I am considering pumping the hot water to the two upstairs sinks as well (and probably another shower in the future)

    I am not sure whether to do this using a separate single impeller pump alongside a double impeller shower pump (after adding Surrey/Warix etc), or a higher pressure twin pump to all. (Probably Monsoon 3 bar - positive or universal)

    My specific uncertainties are:

    1. Is using a single pump here more likely to lead to temperature fluctuations in the shower?
    2. Is there a concern about frequently using a twin impeller pump on one feed only, especially with regard to premature wear?
    3. Are there any considerations about pumping hot water through a TMV against mains fed cold water - ie do I need a Universal pump rather than positive pressure?
    4. The hot water taps may be used at quite low flow - would I therefore be better off with a Universal pump for these in both situations?

    I would much appreciate any opinions.

    Paul
     

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