Shower Lukewarm or Tripping Power? Testing & Replacing Heating Elements

⚠️ SAFETY FIRST: READ BEFORE STARTING

Working on electric showers is dangerous. You are dealing with a high-voltage appliance (240V) and water.

• ISOLATE POWER: Always turn off the electricity at the main consumer unit (fuse box) and pull the isolation cord before removing the shower cover.

• VERIFY DEAD: Use a voltage tester to ensure no power is reaching the unit.

• LEGALS: In the UK, major electrical work in bathrooms is "Part P" regulated. If you are not a competent person or are unsure of these tests, stop and consult a Part P qualified electrician.

• DISCLAIMER: You follow these guides at your own risk. This site and its authors are not liable for any injury, loss, or damage caused by your repairs.

Before opening the unit, follow my [Electrical Safety Isolation Protocol] to avoid a 240V shock

Bit harder to do compared to other jobs but nothing that you cannot do , to test the element use a multimeter set to resistance Omhs scale and test both elements as below my reading were 15 Ohms for one and 12ohms for the other this is normal and good readings for an electric shower heater element . if you get OL it means an element it damaged internally and 0.00 mean short circuit but this would blow you main fuse.

To check readings you have to calculate parallel  resistance of the 2 elements which in this case is 6.67ohms then the formula is V squared / resistance 

So 57600 / 6.67 = 8635.6 / 1000 = 8.6KW this is an 8.5kw so good enough 

Signs of a Failed Element

• The "RCD Trip": If your shower trips the power as soon as you turn the dial to "Hot," the element casing has likely split, allowing water to touch the electrical coil.

• The "Lukewarm Blast": If you have to turn the dial almost to "Scalding" just to get a warm shower, one of your two elements has likely burnt out.

• Visible Damage: If you remove the canister and see "bulging" or white mineral deposits on the terminals, it’s a sign of overheating.

Buy electric shower parts on Ebay UK here

Need a Multimeter for testing try on Ebay UK here

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Heating Element Resistance Values

To test your elements, isolate the power and set your multimeter to the

Ohms ($\Omega$) setting.

Shower Power Rating	Expected Resistance (Combined)	Individual Element Reading
8.5kW	Approx. $6.5\Omega$	$13\Omega -15\Omega$
9.5kW	Approx. $5.8\Omega$	$11\Omega -13\Omega$
10.5kW	Approx. $5.2\Omega$	$10\Omega -12\Omega$

Pro Tip: Most canisters have two elements. If one is dead ("OL" reading), the shower will still work but it will only be lukewarm, even on the high setting

First remove the outlet pipe retaining screws 

and the side retaining screw of the heater can 

then flip it around you can test the element now while in shower or out after 

depends on circumstances 

Just resistance read both heating elements here i have 12 ohm 

and 15 ohms 

Check your measurements its quite easy to tell what your measures are meant to be

Voltage / resistance = Power 230V / ( 12 + 15 ) = 8.5KW 

then undo the neutrals side of element 

Next undo both brown wires to element Lives , and ensure you know which is top and bottom

next i undo screw holding thermal cut out it place 

and pull the cut out free of heater to allow me to pull heater out

when you replace do not forget o-ring 

testing heater out of the shower 

place it back carefully make sure all o-rings are fitted and seal

and all wires are correct and tight 

see video of the whole process below

When buying a replacement, you don't always need to buy the whole 'tank assembly.' You can often just buy the 'heater canister' which saves you £40. Look for the sticker on your current tank to match the kW rating exactly.

Buy electric shower parts on Ebay UK here