The Most Common Mistakes When Installing a DAFI Tankless Water Heater and How to Avoid Them  - A practical guide for anyone who wants to avoid costly mistakes when installing a DAFI heater

The Most Common Mistakes When Installing a DAFI Tankless Water Heater and How to Avoid Them

Incorrect power selection – the classic mistake

This is the kind of mistake that can completely mess up your whole setup. People often choose a water heater “by feel” – because it was on sale, someone recommended it, or it just looked solid. But how much water you want to heat and how quickly you want it heated makes a huge difference. If you're planning to connect your DAFI to a shower and you pick the 3.7 kW model, don’t be surprised when the water comes out lukewarm – especially in winter.

And it's not just about comfort. A heater that's too weak works harder and longer to heat the water, meaning higher electricity use. A model that's too strong can overload your electrical system and trip breakers. This isn’t something you guess. You need to know your water pressure, inlet temperature, pipe length, and real needs.

It’s always worth consulting a professional or at least using a power selection calculator that factors in everything. Don’t risk turning your morning shower into an ice-cold shock.

Skipping the air purge before first startup – a shortcut to failure

This seems like a small thing but can destroy your heater right out of the box. After mounting the unit, you absolutely MUST let water run through it before connecting the power. Not just for a second – give it a solid minute or two. The water needs to flush out all the air inside the heating chamber.

If you don’t, the heating element will switch on “dry.” And that’s a recipe for disaster. Burned-out element, warranty claim, frustration, and days without hot water. The manufacturer clearly states this in the manual – but who really reads manuals, right?

So remember: water first, electricity second. Even if you’re sure the unit was used before – don’t chance it. Open the tap, wait, listen for bubbling. Better to spend one extra minute now than regret a toasted heater later.

Installing in the wrong spot – “It’ll fit somehow” doesn’t cut it

Another classic. People try to squeeze a DAFI heater where there’s neither space nor proper conditions. Like behind a cabinet, inside a shower (yes, really!), above a bathtub, or in a sealed alcove with no ventilation. Then they’re surprised when it steams, leaks, overheats, or just doesn’t work.

The heater should be installed:

• As close as possible to the point of use,
• In a dry, well-ventilated location,
• With easy access for maintenance or replacement,
• Respecting the indicated water flow direction on the housing.

Also keep in mind mounting height – if it’s feeding a sink, it shouldn’t be hanging 2 meters up. The shorter the pipe between the heater and the tap, the less heat loss and the faster the effect.

Don’t get creative. Don’t mount it “wherever it fits.” This isn’t a blender – it’s a high-voltage device under pressure.

Ignoring grounding and electrical safety – asking for trouble

This isn’t an optional detail – it’s a must. Your DAFI water heater must be connected to a grounded power circuit. No exceptions. Otherwise, you’re risking electric shock – and no, that’s not an exaggeration.

Also, the cable thickness matters. For 3.7 kW you’ll need at least 2.5 mm² wires, but for 7.5 kW and up, go with 4 mm² minimum. And you need a dedicated circuit with its own breaker – ideally a residual current device (RCD).

Some people try to plug the heater into a regular wall socket – and then the weird stuff starts: tripped fuses, inconsistent heating, or even electrical fires.

There’s no room for shortcuts here. If you’re not sure whether your installation can handle it – call an electrician. It might cost a few bucks, but it’ll save you major headaches later.

Wrong water connections – sounds silly, but it matters

Lastly, something that seems basic but often causes problems: connecting the water lines backward. Every DAFI heater has markings on the casing showing where to connect the cold water in and where the hot water comes out.

Mix these up? You’ve got a recipe for disaster. Best case, the water won’t flow at all. Worst case – you flood your kitchen or bathroom, because pressure goes the wrong way and valves start failing.

It’s also smart to use a shut-off valve on the inlet. It makes maintenance easier and lets you quickly cut the water in an emergency. Don’t skimp on fittings or valves – spending an extra ten bucks could save you a fortune in repairs.

The installation manual clearly shows what goes where. Don’t wing it. Even if you’ve done plumbing before – each model has its quirks. Better to double-check than deal with a mystery leak.