Can pumping cold water from reservoir into fully heated boiler cause damage?

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#1: Post by mateu »


I'm seeking this information on the web but, couldn't find any answer yet.

I am wondering if pumping cold reservoir water into fully heated boiler could potentially cause any damage to the heating element or the boiler itself. This situation would occur after you drain your boiler empty through the boiling water outlet after heating it up, in a HX machine the water pump would automatically start filling back up the boiler with a cold reservoir water. I am thinking of eg. cracks on the heating element caused by the rapid cooldown due to contact with a cold water being pumped in. Do you think that's remotely possible, or not a chance?

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BaristaBoy E61

#2: Post by BaristaBoy E61 »

Welcome to HB Mat.

If I were partially emptying the boiler via the hot water spigot, I would first turn the machine 'OFF', draw the hot water from the hot water spigot, then wait for it to cool down before refilling to mitigate the risk of heater element damage caused by thermal shock of particularly cold water.

Why take the risk?

"You didn't buy an Espresso Machine - You bought a Chemistry Set!"

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#3: Post by HB »

I know of one vendor who specifically warns to only draw one cup of water at a time and then let the boiler refill to avoid damaging the heating element.

If the boiler is drained from the water tap, the outlet tube should originate from above the heating element so the heating element cannot be exposed to air. So, in theory, the boiler is 1/4 to 1/3 full at all times. That would dampen the thermal shock of introducing reservoir water into the heated boiler.

That said, I'm with BaristaBoy and power off the machine if I'm draining the steam boiler that way (e.g., weekly at the end of a session to flush out excessive minerals).
Dan Kehn

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#4: Post by Nunas »

Like the other's, I'd tread carefully. That said, heating elements burn out from overheating, such as in an empty boiler, not from over cooling. A boiler would not be much different from an electric kettle in this regard. Many's the time I've not had quite enough hot water for tea and have added cold water to a nearly empty kettle. Nothing untoward happened.

mateu (original poster)

#5: Post by mateu (original poster) »

Thank you for sharing the knowledge. I might have screwed that precaution cooldown before pumping the water from reservoir a few times over those 4 years I have my ECM, but I have not noticed any issues, so I guess I have been lucky.

I am asking this because I have not descaled my machine for some years now, decided its a high time to do so, and watched some YT videos, and noticed nobody ever mentions cooling down the boiler before allowing the pump to fill it up again, so it seemed weird to me being aware of the machine internals. Anyway, I'm glad that I've asked, now I will cool it down every time after draining the boiler.

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BaristaBoy E61

#6: Post by BaristaBoy E61 »

If you're descaling your machine completely with citric acid, I'd prepare the mixture and fill the reservoir. I would then do the initial drawing of the steam boiler that only has hot water in it at this point, by turning "OFF" the machine and expel as much water as possible through the hot water spigot.

After cooldown and turning the machine back 'ON' I would draw small amounts of water through the hot water spigot, this time without turning the machine 'OFF'.

It would also be helpful to draw that hot water into a graduated pyrex measuring cup so that the same amount can be drawn without drawing too much. The other thing I would suggest would be to take pictures of the measuring cup's content after each draw to monitor and record by colour your progress to know when you're done and to have a pictorial record and reference for next time.

If you want to either lengthen the time between descaling and perhaps eliminate the process and problems, use only non-scaling water.
"You didn't buy an Espresso Machine - You bought a Chemistry Set!"

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#7: Post by JRising »

Just for another 2 cents worth... Most machines are smart enough not to heat the element while filling, this saves the element from possibly being on when not submerged, so long as everything's working. The original poster was probably about his Technika, so it falls into the category of machines that will not heat while doing a boiler-fill cycle.

Also, when drawing off water through the water valve, most will begin the boiler-fill cycle (if the machine is on) within 6 seconds of the probe being dry, so while the machine is still 2/3 full and long before the element breaks the surface. The cold water squirting into a 2/3 full boiler isn't terribly likely to thermally shock a crack into anything.

mateu (original poster)

#8: Post by mateu (original poster) »

While it is true that boiler is not heating up anymore when its empty, the heating element is still very hot right after emptying the boiler. And while it is true that the pump turns on while you are still emptying the boiler, the tempo of emptying is much faster than the pumps ability to refill it - the water mixing is marginal here. Therefore the concern of cold water being pumped into still-hot boiler with hot heating element is valid, especially when talking about descaling when you have to replace the boiler water entirely. I would not feel comfortable not waiting for it to cool down during such operation. As said, I fully emptied it a few times and allowed the pump to do its job without waiting for cool down, and the machine is full intact, but I just don't feel comfy doing so.