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Hot water heater install.... easy or hard?

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You may receive conflicting advice, "professional installation" installation is the best way, sadly the actual

worker could be an expert or an idiot (like my split aircon "free installation" which in fact was nothing more

than piecework for someone with no flaring tools).


"Point of use" instant heaters can be added as you can afford them and don't require a hot pipe circuit.

If your bathroom and kitchen are close then consider a storage type heater with hot pipe circuit.


Instant water heaters: Can be chosen to suit high or low water pressure, some have a plastic heater

tank that can be dismantled for cleaning, copper tanks are generally sealed throwaways.

Don't buy "bells and whistles" because there may be no spare parts available, 3kw (3,000 watts)

seems fine and won't overload your house electrics.

Choose a model with electrical safety device (not just overheat switch) because stand-alone safety

devices are almost impossible to locate!


Storage water heaters: require more plumbing, choose a model that does not need a cold storage

roof tank.

INTERESTING: In some water districts storage type heaters may only last 3-4 years, usually 

because the sacrificial anode has been consumedf




If you are in a hard water area calcification  or silification block showerheads often, silification does not

dissolve, prick shower heads carefully from inside with a hard wooden (bamboo) toothpick.


Before trusting this with your life, get a knowledgeable trustworthy electrical engineer to inspect it!

If you have calcification in your shower head, just soak it in vinegar and the deposits will disolve.

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I'm assuming Paul is ok with you posting this but for newer members who might see this, be sure to get Paul's approval before posting any kind of advertisement.

ok never mind though i was helping him out... 

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Just make sure the free "installation" is not just the plumbing but also includes the wiring and a positive test for working hot water. I have had several of these "instant" hot water showers installed in my properties in NZ (220v) in all cases they required heavier wiring to switch board and stronger switches and fuses there. The plumber will cheerfully install it and then tell you you need a registered electrician  - who will then tell you about the wiring requirements to wire it up to heat the water. They do not just plug into a power point.

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There are 3 parts to such Water Heater Installation, assuming you want electic heated Hot Water (not Solar heated Hot Water):-

shower-heater-16246-27644-0.jpg supply.jpg

Water and Electricity Supply (UK)
1. separate circuit from consumer unit

2. mains water supply
3. non-return valve
4. shower unit
5. ceiling-mounted double-pole isolating switch
6. mains electric supply (via double-pole switch)

UK Regulations insist on 5., and 3. (on mains water supply 2.)


  1. The Electical Installation
    This ideally requires its own double pole breaker of at least 30A  (good for load up to 6.9kW max) 
    One also needs a Ground/Earth connection, for safety.  If one does not exisit, you need to create one with a ground spike driven into the earth ((preferably in the shade. near drains, so the ground stays damp), and an earthing wire (Green) bolted to that spike and taken to the chassis of the Breaker Cabinet.
    A 3 core cable of 30A capacity from the breaker to where the Heater is to be installed.  No sockets - direct into the Water heater (hence the need for a breaker, so it can be electrically isolated, for installation and repair/replacement).


    The flow of water through the shower unit triggers a switch to turn on the element that heats the water as it passes through. Because there’s so little time to heat the flowing water, a powerful electrical load is required, anything from 6-10.8 KW. This must be supplied by a separate radial circuit, protected by a 30 milliamp RCD 2.

    The electric supply cable must be a minimum 10mm2 twin (two-core) and earth cable. The circuit needs a 45 amp double-pole isolating switch, which is usually a ceiling-mounted type as shown in the diagram opposite. The switch must have a mechanical on-off indicator as well as a neon one. It is also imperative that the shower unit and all metal pipes are bonded to earth. If you are in any doubt about the wiring requirements ask a qualified electrician to advise you. Indeed, you will almost certainly need to get an electrician to bring the new circuit for the shower from the consumer unit.


  2. The Plumbing
    You need a cold water feed, to where the Water heater is to be installed. If it is for a shower, then enough pressure for a good shower will be enough for the heater.  However there should not be too much pressure.  Some Water Heaters come with a flow reducer in the main water flow knob to limit the pressure it it is too high.

    Shut-Off-Valve.gif  Toilet_supply_-_braided.jpg

    I suggest terminating to pipe with a quality valve, like most supply to a toilet.  A stainless steel hose can then connect from that valve to the Inlet pipe/flow tap of the Water Heater.

    If you want Multipoint (ie hot water to more than one outlet, ie Shower and Hot water Taps, then you need to buy i) a Multipoint type Heater, ii) plumb in a 'T" where the bottom connects the the Hot Water outlet and the left and the right to the respective outlets, where the Hot Water is required.  Again it is a good idea to terminate is such angled shut off valves.  Clearly if the Shower is where the Heater is being installed it will only be a short feed to the stop valve and threaded outlet that the shower hose connects to.

    If you are running a hot water pipe to a sink or another room, consider an insulating sleeve over galvanised or copper pipe (especially if being chased into a wall).  Why have the hot water, heating up the concrete!
  3. The Water Heater Installation (Multipoint type perhaps?) 
    This should be purchased before buying/doing the Wiring and Plumbing.

    I strongly advise buying one with built in RCD, that will trip the supply to the heater if a leakage current to ground, is detected.  They usually have a TEST Switch - Use this before using and regulary to test it does cut off and the light on the Heater indicates it is working.
    Read the Instruction with regard to Eletcrical requirements and Water Flow Pressure (Max and Min).  You will also then know what type of pipe fittings for Inlet and outlet are required. and how much wire protruding from the wall to reach the  Terminal block inside and if the waterproof gland takes oval or round 3 core wire and buy the appropriate cable of the correct gauge, long enough to reach the breaker.
    ​Use quality mounts for the screws to go into, that attach the heater to the wall, and I suggest using stainless steel screws, so they wont go rusty.  

These are just suggestions based on my own experience and shortcomings of such water Heaters, Whilst I did an Electronic Engineering Apprenticeship, I did not qualify as a certifed Electrician, but did look at the prevailing IEE Wiring Regulations, before installing an instand heat water Shower in the first 2 bedroom apartment that I bought in 1979 for GBP15,000 on a GBP7,500 Mortgage.  This was long before such DIY installations, were outlawed in the UK!

No one is allowed to do any wiring or plumbing in the UK in Kitchens or bathrooms without the requisite certification and permits. One also has to issued with a Certificate, that goes with any house sale, No certificate for wiring/plumbing in Kitchens and bathrooms, than no sale in the UK, now (from what I have read)!

I am sure any house /apartment, wired to IEE regulations, would meet and ptobably surpass any Philippine Regulations controlling the wiring/plumbing in Kitchens/Bathrooms (if they exist/followed/checked, let alone any certificate given).



Edited by David_LivinginTalisay
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