Now a plumbing question; a long time ago I asked about an under sink
water heater for the kitchen as it took 40 seconds to run hot from the
cylinder upstairs. I want to replace the kitchen hot water completely
and have mains flow, unvented heater but still use the existing sink tap
rather than a separate pipe like the geysers of old. Is this a thing
that can be done? Because the mains flow is poor I am having a 25mm
plastic [i[e mo;ed in from the stop cock in the road next week so when
that is done seems the time to fit it.

I am looking at a reserve of 5-10 litres and 1-1.5kW,any recommendations

ajh <news@loampitsfarm.co.uk> wrote:
> Now a plumbing question; a long time ago I asked about an under sink
> water heater for the kitchen as it took 40 seconds to run hot from the
> cylinder upstairs. I want to replace the kitchen hot water completely
> and have mains flow, unvented heater but still use the existing sink tap
> rather than a separate pipe like the geysers of old. Is this a thing
> that can be done? Because the mains flow is poor I am having a 25mm
> plastic [i[e mo;ed in from the stop cock in the road next week so when
> that is done seems the time to fit it.
>
> I am looking at a reserve of 5-10 litres and 1-1.5kW,any recommendations

I have done something like this in our kitchen for the same (long
distance from hot water tank) reason. However I just run the heater
on the existing hot water feed. It works fine. Mine isn't as big as
you're intending, I just bought the cheapest, simplest possible one
from Screwfix.

--
Chris Green
·

On 18/10/2022 17:52, ajh wrote:
> Now a plumbing question; a long time ago I asked about an under sink
> water heater for the kitchen as it took 40 seconds to run hot from the
> cylinder upstairs.  I want to replace the kitchen  hot water completely
> and have mains flow, unvented heater but still use the existing sink tap
> rather than a separate pipe like the geysers of old. Is this a thing
> that can be done? Because the mains flow is poor  I am having a 25mm
> plastic [i[e mo;ed in from the stop cock in the road next week so when
> that is done seems the time to fit it.
>
> I am looking at a reserve of 5-10 litres and 1-1.5kW,any recommendations

It looks like there is plenty of choice in the 10L unvented type of
product. Heatrae Sadia have a decent enough reputation, but you will pay
a premium for them. e.g.

https://bhl.co.uk/baxi-heatrae-sadia-streamline-under-sink-heater-7-ltr-1-kw-95010280-wd70518.html

--
Cheers,

John.

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On 18/10/2022 19:12, John Rumm wrote:
> On 18/10/2022 17:52, ajh wrote:
>> Now a plumbing question; a long time ago I asked about an under sink
>> water heater for the kitchen as it took 40 seconds to run hot from the
>> cylinder upstairs.  I want to replace the kitchen  hot water
>> completely and have mains flow, unvented heater but still use the
>> existing sink tap rather than a separate pipe like the geysers of old.
>> Is this a thing that can be done? Because the mains flow is poor  I am
>> having a 25mm plastic [i[e mo;ed in from the stop cock in the road
>> next week so when that is done seems the time to fit it.
>>
>> I am looking at a reserve of 5-10 litres and 1-1.5kW,any recommendations
>
> It looks like there is plenty of choice in the 10L unvented type of
> product. Heatrae Sadia have a decent enough reputation, but you will pay
> a premium for them. e.g.
>
> https://bhl.co.uk/baxi-heatrae-sadia-streamline-under-sink-heater-7-ltr-1-kw-95010280-wd70518.html
>
>
>
>
That's the sort of thing, do you know if this has a built in pressure
relief valve and expansion device, the ones I am looking at seem to need
additional external ancillaries which I would rather not have to use?

On 18/10/2022 18:32, Chris Green wrote:
> ajh <news@loampitsfarm.co.uk> wrote:
>> Now a plumbing question; a long time ago I asked about an under sink
>> water heater for the kitchen as it took 40 seconds to run hot from the
>> cylinder upstairs. I want to replace the kitchen hot water completely
>> and have mains flow, unvented heater but still use the existing sink tap
>> rather than a separate pipe like the geysers of old. Is this a thing
>> that can be done? Because the mains flow is poor I am having a 25mm
>> plastic [i[e mo;ed in from the stop cock in the road next week so when
>> that is done seems the time to fit it.
>>
>> I am looking at a reserve of 5-10 litres and 1-1.5kW,any recommendations
>
> I have done something like this in our kitchen for the same (long
> distance from hot water tank) reason. However I just run the heater
> on the existing hot water feed. It works fine. Mine isn't as big as
> you're intending, I just bought the cheapest, simplest possible one
> from Screwfix.
>

I considered that but decided that would mean taking water from the hot
tank where most of the time it would just heat the pipes and go cold.

On 18/10/2022 19:50, ajh wrote:
> On 18/10/2022 18:32, Chris Green wrote:
>> ajh <news@loampitsfarm.co.uk> wrote:
>>> Now a plumbing question; a long time ago I asked about an under sink
>>> water heater for the kitchen as it took 40 seconds to run hot from the
>>> cylinder upstairs.  I want to replace the kitchen  hot water completely
>>> and have mains flow, unvented heater but still use the existing sink tap
>>> rather than a separate pipe like the geysers of old. Is this a thing
>>> that can be done? Because the mains flow is poor  I am having a 25mm
>>> plastic [i[e mo;ed in from the stop cock in the road next week so when
>>> that is done seems the time to fit it.
>>>
>>> I am looking at a reserve of 5-10 litres and 1-1.5kW,any recommendations
>>
>> I have done something like this in our kitchen for the same (long
>> distance from hot water tank) reason.  However I just run the heater
>> on the existing hot water feed.  It works fine.  Mine isn't as big as
>> you're intending, I just bought the cheapest, simplest possible one
>> from Screwfix.
>>
>
> I considered that but decided that would mean taking water from the hot
> tank where most of the time it would just heat the pipes and go cold.

Actually thinking on; John's link seems to be suitable only for vented
taps so for ease of installation it may be better to swap the hot feed
to this pipe for a cold one from the loft tank. This obviates the need
for pressure relief and expansion devices

ajh <news@loampitsfarm.co.uk> wrote:
> On 18/10/2022 19:50, ajh wrote:
> > On 18/10/2022 18:32, Chris Green wrote:
> >> ajh <news@loampitsfarm.co.uk> wrote:
> >>> Now a plumbing question; a long time ago I asked about an under sink
> >>> water heater for the kitchen as it took 40 seconds to run hot from the
> >>> cylinder upstairs.  I want to replace the kitchen  hot water completely
> >>> and have mains flow, unvented heater but still use the existing sink tap
> >>> rather than a separate pipe like the geysers of old. Is this a thing
> >>> that can be done? Because the mains flow is poor  I am having a 25mm
> >>> plastic [i[e mo;ed in from the stop cock in the road next week so when
> >>> that is done seems the time to fit it.
> >>>
> >>> I am looking at a reserve of 5-10 litres and 1-1.5kW,any recommendations
> >>
> >> I have done something like this in our kitchen for the same (long
> >> distance from hot water tank) reason.  However I just run the heater
> >> on the existing hot water feed.  It works fine.  Mine isn't as big as
> >> you're intending, I just bought the cheapest, simplest possible one
> >> from Screwfix.
> >>
> >
> > I considered that but decided that would mean taking water from the hot
> > tank where most of the time it would just heat the pipes and go cold.
>
> Actually thinking on; John's link seems to be suitable only for vented
> taps so for ease of installation it may be better to swap the hot feed
> to this pipe for a cold one from the loft tank. This obviates the need
> for pressure relief and expansion devices

That's why I went for the simplest option of using the hot feed. Our
mains pressure is very high too which as another reason for taking
this route.

--
Chris Green
·

On 18/10/2022 19:49, ajh wrote:
> On 18/10/2022 19:12, John Rumm wrote:
>> On 18/10/2022 17:52, ajh wrote:
>>> Now a plumbing question; a long time ago I asked about an under sink
>>> water heater for the kitchen as it took 40 seconds to run hot from
>>> the cylinder upstairs.  I want to replace the kitchen  hot water
>>> completely and have mains flow, unvented heater but still use the
>>> existing sink tap rather than a separate pipe like the geysers of
>>> old. Is this a thing that can be done? Because the mains flow is
>>> poor  I am having a 25mm plastic [i[e mo;ed in from the stop cock in
>>> the road next week so when that is done seems the time to fit it.
>>>
>>> I am looking at a reserve of 5-10 litres and 1-1.5kW,any recommendations
>>
>> It looks like there is plenty of choice in the 10L unvented type of
>> product. Heatrae Sadia have a decent enough reputation, but you will
>> pay a premium for them. e.g.
>>
>> https://bhl.co.uk/baxi-heatrae-sadia-streamline-under-sink-heater-7-ltr-1-kw-95010280-wd70518.html
>>
>>
>>
> That's the sort of thing, do you know if this has a built in pressure
> relief valve and expansion device, the ones I am looking at seem to need
> additional external ancillaries which I would rather not have to use?

I think anything under 15L is exempt from some aspects of the normal
unvented cylinder requirements.

Looking at the install manual for that one:

https://electricaldealsdirect.co.uk/media/pdfs/Streamline-installation-manual.pdf

Suggests it must be used with vented taps - and that the installer
should "Explain that the water in the Streamline will expand during
heating causing the tap to drip. This is normal and is not a fault with
the Streamline"

(vented taps are not cheap it seems!)

Some basically just push expansion water back up the mains feed. They do
also include a relief valve in the supply pipe. and an over pressure
blow off valve (both of which need to run to a drain via a tundish) but
don't necessarily need the expansion vessel unless the input main
pressure is too high, or there is some kind of check valve in the supply.

Like this one:

https://bhl.co.uk/zip-varipoint-10l-undersink-water-heater-vp103ub-wd69027.html

Install manual here:

https://cdn.plumbnation.co.uk/site/zip-varipoint-ii-over-sink-unvented-15l-water-heater/zip-varipoint-installation--maintenance-and-user-instructions.pdf

--
Cheers,

John.

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In message <41e32j-5f2s1.ln1@esprimo.zbmc.eu>, Chris Green <cl@isbd.net>
writes
>ajh <news@loampitsfarm.co.uk> wrote:
>> On 18/10/2022 19:50, ajh wrote:
>> > On 18/10/2022 18:32, Chris Green wrote:
>> >> ajh <news@loampitsfarm.co.uk> wrote:
>> >>> Now a plumbing question; a long time ago I asked about an under sink
>> >>> water heater for the kitchen as it took 40 seconds to run hot from the
>> >>> cylinder upstairs.  I want to replace the kitchen  hot water completely
>> >>> and have mains flow, unvented heater but still use the existing sink tap
>> >>> rather than a separate pipe like the geysers of old. Is this a thing
>> >>> that can be done? Because the mains flow is poor  I am having a 25mm
>> >>> plastic [i[e mo;ed in from the stop cock in the road next week so when
>> >>> that is done seems the time to fit it.
>> >>>
>> >>> I am looking at a reserve of 5-10 litres and 1-1.5kW,any recommendations
>> >>
>> >> I have done something like this in our kitchen for the same (long
>> >> distance from hot water tank) reason.  However I just run the heater
>> >> on the existing hot water feed.  It works fine.  Mine isn't as big as
>> >> you're intending, I just bought the cheapest, simplest possible one
>> >> from Screwfix.
>> >>
>> >
>> > I considered that but decided that would mean taking water from the hot
>> > tank where most of the time it would just heat the pipes and go cold.
>>
>> Actually thinking on; John's link seems to be suitable only for vented
>> taps so for ease of installation it may be better to swap the hot feed
>> to this pipe for a cold one from the loft tank. This obviates the need
>> for pressure relief and expansion devices
>
>That's why I went for the simplest option of using the hot feed. Our
>mains pressure is very high too which as another reason for taking
>this route.

I think ajh is *down South* so future water softener might point to hot
tank source.
>

--
Tim Lamb

On 18/10/2022 17:52, ajh wrote:
> Now a plumbing question; a long time ago I asked about an under sink
> water heater for the kitchen as it took 40 seconds to run hot from the
> cylinder upstairs.  I want to replace the kitchen  hot water completely
> and have mains flow, unvented heater but still use the existing sink tap
> rather than a separate pipe like the geysers of old. Is this a thing
> that can be done? Because the mains flow is poor  I am having a 25mm
> plastic [i[e mo;ed in from the stop cock in the road next week so when
> that is done seems the time to fit it.
>
> I am looking at a reserve of 5-10 litres and 1-1.5kW,any recommendations

I had exactly the same problem, and installed a Quooker water heater.
That stores 7 litres of boiling water under pressure in an insulated
container. It has a 3kW heater, so it doesn't take very long to re-heat
if all the hot water has been used. Mine has two outlets - a direct one
for a boiling water tap (supplied) and one via a supplied mixing valve
to feed the normal hot tap. It has a (supplied) pressure relief valve
whose output is connected to the sink drain.

I've had it for several years now, and it's still going strong despite
being in a hard water area. There's more than adequate mixed water for
washing up, and it's useful being able to make tea and coffee without
needing to boil a kettle.

It didn't come cheap, though!
--
Cheers,
Roger

On Tuesday, 18 October 2022 at 18:33:07 UTC+1, Chris Green wrote:

> I have done something like this in our kitchen for the same (long
> distance from hot water tank) reason. However I just run the heater
> on the existing hot water feed.
> Chris Green
> ·
But that means you're heating water that will just sit in the pipe.

Bill

On Tuesday, 18 October 2022 at 23:56:45 UTC+1, John Rumm wrote:
>
> > That's the sort of thing, do you know if this has a built in pressure
> > relief valve and expansion device, the ones I am looking at seem to need
> > additional external ancillaries which I would rather not have to use?
> I think anything under 15L is exempt from some aspects of the normal
> unvented cylinder requirements.

Mine has a separate expansion tank.

Bill

On 19/10/2022 16:46, wrights...@f2s.com wrote:
> On Tuesday, 18 October 2022 at 18:33:07 UTC+1, Chris Green wrote:
>
>> I have done something like this in our kitchen for the same (long
>> distance from hot water tank) reason. However I just run the heater
>> on the existing hot water feed.
>> Chris Green
>> ·
> But that means you're heating water that will just sit in the pipe.

I did the same, as it's such a simple setup. It also means that if you
want large quantities of hot water, you can without waiting for the
water to heat up again.

Perhaps best to lag the pipes?

wrights...@f2s.com <wrightsaerials@f2s.com> wrote:
> On Tuesday, 18 October 2022 at 18:33:07 UTC+1, Chris Green wrote:
>
> > I have done something like this in our kitchen for the same (long
> > distance from hot water tank) reason. However I just run the heater
> > on the existing hot water feed.
> > Chris Green
> > ·
> But that means you're heating water that will just sit in the pipe.
>
Yes, but it's still far less wasted heat than filling the whole length
of the pipe with hot water.

--
Chris Green
·

On 19/10/2022 16:49, wrights...@f2s.com wrote:
> On Tuesday, 18 October 2022 at 23:56:45 UTC+1, John Rumm wrote:
>>
>>> That's the sort of thing, do you know if this has a built in pressure
>>> relief valve and expansion device, the ones I am looking at seem to need
>>> additional external ancillaries which I would rather not have to use?
>> I think anything under 15L is exempt from some aspects of the normal
>> unvented cylinder requirements.
>
> Mine has a separate expansion tank.

With small capacity cylinders you can often avoid one, however in some
cases[1] you may still need one.

[1] mains pressure too high, or non return valve in the supply being
common.

--
Cheers,

John.

/=================================================================\
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\=================================================================/

On 18/10/2022 21:13, Chris Green wrote:
> ajh <news@loampitsfarm.co.uk> wrote:
>> On 18/10/2022 19:50, ajh wrote:
>>> On 18/10/2022 18:32, Chris Green wrote:
>>>> ajh <news@loampitsfarm.co.uk> wrote:
>>>>> Now a plumbing question; a long time ago I asked about an under sink
>>>>> water heater for the kitchen as it took 40 seconds to run hot from the
>>>>> cylinder upstairs.  I want to replace the kitchen  hot water completely
>>>>> and have mains flow, unvented heater but still use the existing sink tap
>>>>> rather than a separate pipe like the geysers of old. Is this a thing
>>>>> that can be done? Because the mains flow is poor  I am having a 25mm
>>>>> plastic [i[e mo;ed in from the stop cock in the road next week so when
>>>>> that is done seems the time to fit it.
>>>>>
>>>>> I am looking at a reserve of 5-10 litres and 1-1.5kW,any recommendations
>>>>
>>>> I have done something like this in our kitchen for the same (long
>>>> distance from hot water tank) reason.  However I just run the heater
>>>> on the existing hot water feed.  It works fine.  Mine isn't as big as
>>>> you're intending, I just bought the cheapest, simplest possible one
>>>> from Screwfix.
>>>>
>>>
>>> I considered that but decided that would mean taking water from the hot
>>> tank where most of the time it would just heat the pipes and go cold.
>>
>> Actually thinking on; John's link seems to be suitable only for vented
>> taps so for ease of installation it may be better to swap the hot feed
>> to this pipe for a cold one from the loft tank. This obviates the need
>> for pressure relief and expansion devices
>
> That's why I went for the simplest option of using the hot feed. Our
> mains pressure is very high too which as another reason for taking
> this route.
>

Yes simple may well trump total efficiency here and in the summer the
hot tank is not gas heated so no loss of money.

It may well still be worth swapping the current hot water pipe with a
cold feed which may well be possible under the floorboards in the bathroom.

Yes Tim the water is hard here but I do not want to fit a water
softener, I will just see how bad the scale gets.

On 19/10/2022 18:26, ajh wrote:
> On 18/10/2022 21:13, Chris Green wrote:
>> ajh <news@loampitsfarm.co.uk> wrote:
>>> On 18/10/2022 19:50, ajh wrote:
>>>> On 18/10/2022 18:32, Chris Green wrote:
>>>>> ajh <news@loampitsfarm.co.uk> wrote:
>>>>>> Now a plumbing question; a long time ago I asked about an under sink
>>>>>> water heater for the kitchen as it took 40 seconds to run hot from
>>>>>> the
>>>>>> cylinder upstairs.  I want to replace the kitchen  hot water
>>>>>> completely
>>>>>> and have mains flow, unvented heater but still use the existing
>>>>>> sink tap
>>>>>> rather than a separate pipe like the geysers of old. Is this a thing
>>>>>> that can be done? Because the mains flow is poor  I am having a 25mm
>>>>>> plastic [i[e mo;ed in from the stop cock in the road next week so
>>>>>> when
>>>>>> that is done seems the time to fit it.
>>>>>>
>>>>>> I am looking at a reserve of 5-10 litres and 1-1.5kW,any
>>>>>> recommendations
>>>>>
>>>>> I have done something like this in our kitchen for the same (long
>>>>> distance from hot water tank) reason.  However I just run the heater
>>>>> on the existing hot water feed.  It works fine.  Mine isn't as big as
>>>>> you're intending, I just bought the cheapest, simplest possible one
>>>>> from Screwfix.
>>>>>
>>>>
>>>> I considered that but decided that would mean taking water from the hot
>>>> tank where most of the time it would just heat the pipes and go cold.
>>>
>>> Actually thinking on; John's link seems to be suitable only for vented
>>> taps so for ease of installation it may be better to swap the hot feed
>>> to this pipe for a cold one from the loft tank. This obviates the need
>>> for pressure relief and expansion devices
>>
>> That's why I went for the simplest option of using the hot feed. Our
>> mains pressure is very high too which as another reason for taking
>> this route.
>>
>
> Yes simple may well trump total efficiency here and in the summer the
> hot tank is not gas heated so no loss of money.
>
> It may well still be worth swapping the current hot water pipe with a
> cold feed which may well be possible under the floorboards in the bathroom.
>
> Yes Tim the water is hard here but I do not want to fit a water
> softener, I will just see how bad the scale gets.

You could fit a phosphate dosing unit in front of it - it does not
remove the hardness, but reduces the amount that precipitates out of the
water when it is heated.

--
Cheers,

John.

/=================================================================\
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\=================================================================/

On Wednesday, 19 October 2022 at 17:33:07 UTC+1, Chris Green wrote:
> wrights...@f2s.com <wrights...@f2s.com> wrote:
> > On Tuesday, 18 October 2022 at 18:33:07 UTC+1, Chris Green wrote:
> >
> > > I have done something like this in our kitchen for the same (long
> > > distance from hot water tank) reason. However I just run the heater
> > > on the existing hot water feed.
> > > Chris Green
> > > ·
> > But that means you're heating water that will just sit in the pipe.
> >
> Yes, but it's still far less wasted heat than filling the whole length
> of the pipe with hot water.
>
> --
> Chris Green
> ·
When you stop drawing hot water the hot water in the pipe will either have reached the under counter heater or it won't have. If it has reached it the whole pipe will have standing hot water in it. If it hasn't reached it there's no point in using the hot supply.
Bill