I have owned and enjoyed a Rocket Espresso Giotto Professional for roughly year. Over the past several days, the Giotto has started to produce a slight whistling sound--slightly more pronounced on pressure discharged, but also present during recharge. It is difficult to say but the pressure discharge seems a bit more gradual and slower than in the past. I'd love to have someone better versed with HX machines to advise whether this merits concern and what's the likely cause? Thank you in advance.

Whistling sounds are made by gas, not liquid, and are much more likely to issue from the boiler than from the group of an espresso machine. Take off the case and check for small steam leaks.

To elaborate on Jim's diagnosis, it's easier to locate the sound precisely by listening through a tube (e.g., from a roll of paper towels, turkey baster with bulb removed). Check that the steam boiler pressure is normal; it may be the over-pressure safety valve starting to crack open (usually between 1.6 and 2.0 bar).

The thread "How do I detect a steam leak?" (CoffeeGeek) offers other suggestions on finding the cause. Of course, remember to UNPLUG the machine before removing the casing and don't fiddle with fittings while the boiler is pressurized!

Thank you for your excellent suggestions and sage advice. The boiler pressure is absolutely normal as is cycling. I guess the next step is to open her up.

Just to close the loop. When I opened the Giotto up, the cause was obvious. The hissing and steam emanated from the pressure relief valve, pictured below. Simply by pressed the valve a couple of times, I was able to properly re-seat the relief valve. This solved the problem and eliminated the whistle.



Do you have any idea why this would occur? Seattle Coffee, my retailer, suggested the cause could have been "build up". As this Giotto is pumped-in version and I have a Chris Coffee water softener, conditioner and carbon block installed, I question this conclusion. Besides random error, is there another possible cause? Second, should I descale regardless of the softening and conditioning?

Thanks again for your help.

thomgonzales wrote:Seattle Coffee, my retailer, suggested the cause could have been "build up"... I question this conclusion.

I cannot tell from your postage stamp-sized photo, but I assume you refer to the vacuum breaker. Dirt or scale can prevent it from sealing, resulting in the hissing/whistling sound you described. Clean it by soaking it in vinegar / citric acid (needless to say, only work on the boiler while it's cool / depressurized). If it continues to leak, replace it.

Below are two common vacuum breakers:


Two common vacuum breakers - the second is less likely to stick

thomgonzales wrote:Second, should I descale regardless of the softening and conditioning?

I recommend checking for scale and then deciding if the extra effort is justified.

The hissing and steam emanated from the pressure relief valve, pictured below.

Here is another pic of internals very similar to yours. Item 1 is the safety relief valve, TYPICALLY set to relieve at boiler pressures of anywhere from 1.5 to 2.5 bar.



Item 2 is the vacuum breaker valve, which "hisses and whistles" until the boiler pressure hits ABOUT 0.2 bar on its way up to ABOUT 1.10 - 1.20 bar.

Is the culprit Item 1 or Item 2 ?

Without a doubt, both of your photos are better than mine. It's the second in the former and #2 in the latter notes. I gave the machine a thorough descale last night.