Questions about under counter water heaters

Discussion in 'Plumbers' Talk' started by DaveHerts, Aug 19, 2017.

  1. DaveHerts

    DaveHerts Member

    So, I am building out my coffee shop and it only has cold water supply and no gas. The current mini kitchen has a water heater under the sink and some kind of small tank. Not sure what this is for?

    I need to heat enough water for two more sinks. Is there a good, commercial grade under counter water heater that could supply two sinks? I also notice that the water heater has some kind of fancy valve attached. What is this for?
     
  2. just pumps

    just pumps Screwfix Select

    With the kind of water heater you are talking about you need someone with the correct qualification to advise carry out the work.
     
  3. DaveHerts

    DaveHerts Member

    So would that be a plumber or electrician?
     
  4. DIYDave.

    DIYDave. Screwfix Select

    So it sounds like you may have this type of electric water heater at present, heats a quantity of water to set temp then stores it. Tank tops up with cold water and reheats when you open the hot tap and / or thermostat kick in when stored water drops below set temp

    http://www.screwfix.com/p/ariston-andris-lux-3kw-15ltr-undersink-water-heater/2371g

    The 'small tank' you mention is probably an expansion vessel. May look different or another colour but as hot water expands, it gives the water somewhere to expand into as the heater, pipes and tap is basically a sealed system (with the tap off)

    http://www.screwfix.com/p/reflex-expansion-vessel-8ltr/2109r

    The fancy valve will be a PRV - Pressure Release Valve, and will be vented either outside or into a tun dish, should something go wrong with the heater and the pressure rises to above the pre set level - again may look different to this one

    http://www.screwfix.com/p/honeywell-pressure-reducing-valve-15mm/7978j

    That's it from me as i'm only diy
    As above, you really need a decent plumber to advise, especially as this is in a commercial premises and usage will hopefully be high (if ur busy) :)
    Likely that an electrician may also be needed if supply needs upgrading

    Good luck
     
  5. MGW

    MGW Screwfix Select

    I wanted many years ago to get hot water on tap in my caravan, I was given an old under counter water heater, and I found the idea was to use a special tap, this turned the cold water feed on and off to the mini heater and forced the hot water out of a pipe which was always open, this was easy to convert for the caravan using non return valves and Y connectors I had two taps at the front which when turned on caused hot water or cold to come out of a single pipe at rear into the sink.[​IMG]

    However as the cold water warmed up, the pipe at back of sink would drip as water expanded. Because of this cheap method it was not possible to direct the water to the toilet sink as well. It held 7 litres of water, and the element was swapped from 3kW to 1KW and it provided all the hot water I needed until the caravan was sold. It never ran cold under normal use. The element could be rotated to allow for how the unit was mounted, and water would stay hot for 24 hours without a supply, very well insulated.

    I expect the special taps were expensive, but with only 12 volt pump pressure I did not need them. They were standard fitting in porta cabins I got my because threads were damaged on the pipes but I just cut them off and used plastic flexible pipe and jubilee clips.

    To move from these simple units to a unit able to supply 2 or more taps becomes expensive, and so even with two sinks, often they just fitted 2 units, you needed to supply 3 sinks or more before it was worth moving to the more expensive units, the modern method seems to be using instant water heaters, these need a bigger supply, the 1kW unit I had only worked because there was a store of 7 litres of water.

    The whole reason to use the units with 7 litre tanks in porta cabins was they only needed 1 or 3 kW depending on version, the instant type are often 7 kW or more, so first consideration is what it will cost to get the supply to the heater. Today there are loads on new regulations, not sure if the old system I used is still made?
     
  6. Dave is right. It'll be an expansion vessel and a relief valve. You do not need a certificate to install this type of water heater as long as it's less than 15l. It's a good idea to get someone who knows what they're doing though as they have the potential to go badly wrong if not installed correctly. 15l is more than enough for two sinks in most applications.
     
  7. just pumps

    just pumps Screwfix Select

  8. Yes G3 applies but it is not notifiable and a certificate is not required if under 15l. Page 8.
     
  9. just pumps

    just pumps Screwfix Select

    I was taking it to be you must hold the G3 cert to be able to install these in reply to your post #6.
     

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