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Perfect 55 Instant Undersink Instant Water Heater, 5.5KW

£119.99 inc VAT
£99.99 exc VAT

Perfect 55 Instant Undersink Instant Water Heater, 5.5KW

Produces hot water to serve lightly used kitchen sinks and en suite wash basins

27 reviews
£119.99 inc VAT
£99.99 exc VAT

Order now for delivery 24th April

  • Small & space-saving - provides instant hot water to basins and sinks
  • Powerful, compact water heater - ideal for bathrooms, kitchens and cloakrooms
  • High performance and reliability - produces hotter water for a faster flow rate
  • Save water and energy and cut down on waste
  • Optimum performance with spray fitting taps but suitable for use with any taps
See more product details
  • In stock
  • Warranty: 2 Years
  • 30 day money-back guarantee
  • Product Code: 133365
  • Have a question? Call 0800 091 3171

Product information

Power: 5.5 kW
Brand: HSD
Height: 15.2 cm
Width: 13.5 cm
Depth: 7.2 cm
Weight: 0.9 kg
  • This undersink instant hot water heater is a small, space saving model to provide instant hot water for basins and sinks in bathrooms, kitchens and cloak rooms 
  • With the impressive output of 5.5kW, this compact water heater produces hotter water overall and hotter water for a faster flow rate than smaller units, including the perfect 35 and 45 units
  • Using the latest in water heater design work, these units work by heating water as it runs through the unit (as you demand it) rather than heating a set amount of water. An electronic heating element heats the water working under permanent pressure (6.5 bar) for high performance and reliability
  • Instant water heaters take away the inefficiency of heating many litres of water before hot water is produced
  • These reactive units save so much water and energy and cut down on waste wherever they are used
  • With its small size, the Perfect 55 water heater can sit under a sink throughout the home and will quietly cut your energy bills
  • Non vented unit that is suitable for use with any taps with optimum performance with spray fitting taps
  • Minimum water pressure required 10psi or 1.0 bar
  • These units will not fill a bath or provide a shower with hot water
  • Cold water inlet temperature during winter based on 15C
  • Cold water inlet temperature during summer based on 20C
  • 25 amps fuse needed.


Rating 4.7 out of 5 based on 27 reviews.
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Tim Metford
Great product at a sensible price. Quite easy to install and it works a treat! The flow rate out of the hot tap is much better than I expected, so handwashing is a breeze with the instant hot water instead of waiting ages for the boiler to send it through.
6 Nov 2018
Really happy with this. Used in a log cabin that takes a feed from the mains in the house. Not overly powerful but completely acceptable given the power on the mains feed. It gets nice and warm almost instantly.
29 Aug 2018
D I Jones
Neat little unit. Easy to install. Good water temperature.
23 Jul 2018
Jim O'Neil
Excellent water heater good flow rate.
22 Jun 2018
Yvonne Gallagher
Excellent, works well and was easily fitted by competent DIYer!
25 May 2017
Clare Ereira
Fantastic product. Takes up hardly any space under the sink, and means we now get hot water in our kitchen within seconds rather than having to run the tap for ages. The water pressure is lower than getting water direct from the boiler, but this means less wasted water, and it's hot enough to wash up in. We have now bought a 3.5kw one to go under our very tiny downstairs toilet sink, and hope this will also do the job.
8 Sep 2016
Leslie, Cheshire
Very pleased with the previous one I purchased and expect the same great result from this one.
20 Aug 2016
Hazhar, East Riding Of Yorkshire
A great heater, much better than expected. You only have to count until three and you have hot water. Brilliant, highly recommended.
8 Oct 2014
Mr Knight, South Yorks
good product in use
29 Jan 2013
Donald, West Sussex
excellent product, easy to fit, works very well. fast efficient service, would certainly use you again
6 Aug 2012

Documents & Instructions

Frequently asked questions

I need an under sink water heater for use in a shed that in winter may get below freezing. Does the Perfect 50 come with frost protection, or does it not need it, or would I be advised to drain the heater down before the onset of winter?
This unit is not designed for outdoor use.
Our building has no gas supply and no water tank in the loft. Currently hot water is supplied via a Zip under sink 15 litre tank which gets switched on as needed. People have complained that there is not enough hot water to wash up after a 2 course meal
Unfortunately this item would not be suitable for what you are needing.
How many liters is the perfect 50?
The Perfect 50 is an instantaneous unit. This means that it produces hot water on demand and doesn't preheat a set  amount of water.
hi I want it to work a sink for washing up in a road side porta cabin cafe i am worried about low water pressure i have a 25ltr tank with a submersible pump of which is a small caravan whale type. regards Roger
This unit is an instant water heater therefore it does not have a tank to hold water. The minimum water pressure this operates from is 1.0 bar. For full product information please click on the PDF under the section on the product page instructions and informational documents to view the full unit instructions.  
hi my name is enrico i have 3 barber shop 2 of them have no hot water. friend of mine recomend you and advised me one of the undersink hot water system . as will be used for washing hair which product you recomend for me for my kitchen and basin which is
This unit would be fine for your kitchen sink but you could not wash hair with this unit as it is not powerful enough and would burn the element out as it would be over used. 153822 would be the type of unit required these units power showers and that is the type you would require for washing hair. These need to be spurred in by a qualified plumber and electrician. 
Does the unit automatically come on when the basin tap is turned on, or does the unit have to be switched on before using the taps?
The unit automatically comes on when the tap is turned on. 
Can this heater be connected to the hot water pipe? reason is we have a bungalow where the cylinder is a long way from the kitchen hence large amount of water in the pipework has to run before hot reaches the tap. thanks
No these units have to be connected to the mains cold feed only. 
Figure 2 in the Wijas installation guide suggests I could connect to a ring main. Is this true for the 5kW?
This is not suitable for a ring main as you require special 6mm cable.
Hi, need a heater to run a shower in a converted shed, water comes in from mains plastic pipe and 15mm copper in the shed has been lagged ,would this be powerful enough to heat? have a 6mm cable and 32a fuse in the distribution board many thanks tony
This unit is the correct one to comply with your specification for a shower on a single outlet.
How many Amps does the Perfect 50 pull as we live in a caravan and can only draw 30amps max.
21.7 amps fuse needed.
If the unit is suppliying a mixer or monobloc tap does it need to have its own cold supply? Thank you.
Only one cold water supply is needed, but you will have to T off from this supply to go to the water heater, to create a supply to the warm tap,  and still allowing the same supply to continue to the cold tap. On some Monobloc taps, the cold water may need to be slowed down to balance with the flow rate of the warm water. If you would like more information please call 08000913171.
The instruction manual only shows minimum cross section for 5Kw what is minimum cross section and fuse for 5.5Kw? I want to use this with a basin which has separate hot and cold taps not a mixer tap. Is this suitable?
The minimum stated factory specifications for the 5.5kw Perfect 55 is 23.9A fuse and the appropriate cable for this is a 2.5mm squared cable. However, we recommend you confirm this with a qualified electrician, as individual requirements are different. You can use this water heater to supply water to a separate hot water tap.
I have to replace a rusted Hyco under-sink heater which uses an expansion vessel. It supplies two toilet hand wash basins. Would this do the job? Mike Cookson
This water heater would be suitable to supply water to two hand wash basins. However, if they are to be used at the same time, this will effect the flow rate (but not the temperature) going to each sink. If this is not suitable for your needs, please see product codes 107638 or 228763, which are suitable for multiple outlets.
Is the product suitable for a small (25ft) boat? Is a minimum water pressure required?
Unfortunately this would not be suitable for a small boat. This water heater is mains cold water feed only. The minimum water pressure required is 0.75BAR (or 10psi).
Do you know if these are legionella compliant?
Legionella bacteria need a continuous temperature of between 20 and 50 degrees in stored water to grow. As the instantaneous water heaters do not have any water storage, there is no risk of the Legionella bacteria to grow.
Can I connect 2 sinks to one of these units? Unlikely both taps used at once and no problem if they are and water is only Luke warm. Sinks are one metre apart.
We would recommend two heaters, one per tap/basin. However, one could be connected to two basins if only one basin was used at a time.
what is the flow rate at it's hottest if running continuously ?
The flow rate at its hottest temperature (64 degrees Celsius) is 1.5L per minute.
How does the unit cope with hard water? Do I need to fit a descaler or does it not get hot enough to be a problem?
This instant water heater copes extremely well with hard water. Because it doesn\'t keep stored water at high temperatures, there is no water evapouration involved, therefore no limescale build up.
Would this be ok to wash dishes in a sink ( rather than turning on an immersion switch for hours)
Yes, this water heater can be used to wash dishes in a sink. However, this is for light use only.
I have a log cabin in my garden and want to put a sink in it with warm/hot water to wash up in. Would this water heater do the job?
As long as the log cabin has mains electricity and mains water, the water heater will be suitable.
Can I fit this to any bathroom sink tap?
You cannot use this water heater with thermostatic sink taps. Standard taps, including mixer taps, can be used.
I want to change my old under sink water heater in the kitchen & want to know if your units allow us to use normal taps. Currently ours has a long spindle going down into the hot water pipe & this is a pain.
This water heater can be used with normal taps. You can use either a separate hot and cold tap or a mixer tap (not thermostatic).
Can this be wired in with 6mm cable as that's the cable that is already in place
This would need to be wired into a juction and reduced to 4mm 2.5 cable.
Building a tinyhouse would,would the 55 be suitable under the sink,water fed via 12v submerged pump in water tank.

This would be suitable if your pump had the power to deliver at least 1 bar of pressure.  

Please note that an HVLP (High Volume Low Pressure) pump would not be adequate for this water heater. 



Where is the thermal protection button in the perfect 5000 model
It is in the centre of the unit between the connections.
Would this affect drinking water from tap
No. Your cold water will stay the same.
Do I need an expansion tank in the plumbing system is unvented
As this is an instant water heater and does not hold any water, an expansion vessel is not required. 
Can this water heater temperature be adjusted Regards
The temperature flow rate is based on inlet temperature 15C 
3ltr minute is approximately 41C
2.5ltr minute is approximately 46c
2ltr minute is approximately 54c
1.5ltr minute is approximately 64c+
What is the maximum water pressure for this unit. Will it cope with being fitted close to the mains supply?
The maximum water pressure for this unit is 10 bar. The unit can be fitted close to the mains supply.
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