Combi + Delayed Hot Water to Bathroom

Hi,

just had a Baxi Duotec 28 installed in a bungalow. Seems fine.

The distance between the boiler in the kitchen and and the bathroom is about 20 feet, though I guess the pipes go up into the loft, etc. It takes about 30-40 seconds and a lot of water until it starts to get hot. I supposed there's cold water in the pipe.

I just wondered what the best course of action would be to give more "instant" hot water. I've seen these tankless water heaters that can go under a sink (maybe in a vanity unit). Plumber says they're ok but was interested in other points of view.

Thanks,
Ed.

Comments

  • matelodave
    matelodave Posts: 8,586
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    edited 17 November 2017 at 4:29PM
    I'm guessing that you pay around 3p a unit for gas and around 12-15p for leccy so it will cost you about four times as much to heat your hot water with an undersink heater.

    An instantaneous one that will plug into a normal socket (assuming that you've got one adjacent to the sink) rated at 3kw will give you a pathetic flow rate. Even a 9kwh shower which needs it's own high current circuit wouldn't be significantly better out of a tap - they work because the shower head has very, few very small holes - try one with a proper shower head.

    The alternative is a 10-15 litre storage under sink storage heater - you can get them for about £90+ would still need to be plumbed in and would require a 13a power supply.

    You could save time, water and energy by only using hot water when you are having a proper wash or washing up, rather than running the hot tap just to rinse your hands or dishes.

    Have you actually measured the amount of water you are wasting (probably a couple of pence worth) and then looked at the cost of getting and undersink unit installed and worked out the economics of it. You could save the water in a jug and use it to flush the loo or water plants

    It's up to you to decide whether the hassle and cost of getting one plumbed in and connected to the power supply is worth half a minute of your time a couple of times a day?
    Never under estimate the power of stupid people in large numbers
  • Cardew
    Cardew Posts: 29,036
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    Ed_Zep wrote: »
    Hi,

    though I guess the pipes go up into the loft, etc.

    How long does the hot water take to reach kitchen taps?

    Are you sure the hot water pipe goes into the loft?

    I appreciate that it is sometimes unavoidable because of the layout but it is not to be recommended. If it is in the loft it will need lagging and all the hot water in the pipe will cool down.

    Much as it is annoying, I think you will have to put up with the issue. The few pence you lose will not justify the capital expenditure and running costs of an electrical solution.
  • matelodave
    matelodave Posts: 8,586
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    edited 18 November 2017 at 9:27AM
    We've got our hot and cold feeds to both the kitchen and bathroom through the loft as there's no otherway of getting them through the place without crossing the backdoor and kitchen window.

    The pipe run is about 33ft and the pipes are well insulated and run under the loft insulation and it takes about 30 secs for the hot to get through. We lose just under 2.5 litres before the tap gets hot. (just measured it) I thought it was more but we've got flow restrictors on the tap outlets so they only deliver around 5 lpm.
    Never under estimate the power of stupid people in large numbers
  • Cardew
    Cardew Posts: 29,036
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    matelodave wrote: »

    The pipe run is about 33ft and the pipes are well insulated and run under the loft insulation and it takes about 30 secs for the hot to get through and we lose between 4-5 litre before the tap gets hot.

    With a combi there is always a delay before the hot water gets to the taps. I have a combi in an annex. Even though the sink and bath are less than 6 ft away there is still a couple of litres 'wasted'.

    Like some combis ours has a small internal tank in which water can be kept warm to overcome the delay, but there is still cold water in the pipes that has to be run off. I don't use this internal tank as we don't use the annex much, and someone staying there commented that the boiler fired up for a minute or so in the middle of the night - to top up the tank I assume.
  • jk0
    jk0 Posts: 3,479
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    Do what I do:

    I put the plug in main bowl and small bowl. I run the cold 'slug' into the small bowl, and use that for rinsing the dishes after giving them a rub in the main bowl.
  • boliston
    boliston Posts: 3,012
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    some combis have a pre-heat function where they heat a small amount of hot water and store it - i have disabled mine as i found it annoying but it does mean less wait for hot water
  • Ed_Zep
    Ed_Zep Posts: 340 Forumite
    A belated thanks for all the replies.

    I'm going to put up with it. As someone said, it's not worth the expense of getting a water heater.

    One idea I had was to change the 22mm pipe for a 15mm one. As
    volume=π r² h, I've calculated there should be less than 1/2 the amount
    of cold water to run through in the 15mm pipe.
  • Or don't turn the tap any more than half way.
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