Ariston water heater: 5-second delay means cold water in the shower

Five seconds of flame that ruin the shower

A user reports that his Ariston Blu Control 11-litre natural gas water heater, bought in October last year, takes five seconds to light the flame from the moment the tap is peine. According to his account, when he closes the tap to lather up and reopens it, the water comes out hot for an instant, then cold for five or ten seconds, and only then returns to temperature. Customer service, he says, first spoke of one or two seconds and then justified the five on safety grounds.

The user describes how the same thing happens in the kitchen, with the heater about two metres from the sink: closing and reopening the tap within a fraction of a second is enough for the water to go from scalding to cold. His conclusion is that **the ignition delay is what introduces the cold water**, not the cooling of the pipe.

Is it normal for a water heater to take five seconds to light?

Other participants contribute experiences with different equipment. A user with a Roca boiler describes "several seconds" between opening the tap and the unit starting up, and considers that five is not an eternity. Another, with a Vaillant, confirms the same behaviour when shutting off and reopening, and adds that the timing of the servo motor that acts on the pilot igniter is also correct. In other words: **the pattern repeats across different brands**, which weakens the theory of an isolated defect but not that of a design that could be improved.

The customer service argument, as the user tells it, deserves separate analysis. First one or two seconds; then, that the sparks have to be confirmed before opening the gas. The sequence —spark, verification, gas, ignition— is plausible as a safety protocol, but it leaves a gap: **if the protocol was always this, the first answer was false**. And if the first one was right, the second is an excuse. Neither of the two reassures the person who paid for the unit.

The water you waste while lathering up

The most common solution is the most uncomfortable one: not closing the tap. Letting the water run during the thirty or sixty seconds of lathering avoids the cold-water cycle. The owner rejects it on principle —"it seems like a waste to me"— and there lies the crux of the matter: **the user pays twice**, in gas and in water, for a problem he attributes to the equipment. The storage tank alternative also comes up, with its own fine print: whoever raises it admits that for a full bath the tank falls short.

The full calculation of what is lost in each shower, with the close-and-reopen cycle repeated, is the kind of sum nobody does and that changes the perception of the problem. For now, the disagreement remains open between those who see normal operation of instant hot water production and those who demand a faster ignition from the brand.

The prediction, with reservations: until the manufacturer publishes the exact ignition sequence and its timings, each user will keep negotiating with their installer the boundary between safety and comfort. And the cold water will keep going down the drain.