Do you have a picture of the valve?
I'd rather it fail by leaking than by not opening. If it's adjustable, it might take a small tweak; you can verify the setting an operation with an air compressor.

If there's any doubt, replace it- you probably will need a crush washer.

Certainly, replace the copper sealing washer (and get a few spares) if you can. But that may not be enough, so I would have some PTFE tape on hand just in case. When I replaced a thermistor (albeit on the brew boiler), I had to use the tape as well, twisted into a string and wrapped several times tightly into the shoulder of the male fitting. I have to admit that I am not the first to think of this: whether by necessity or for insurance, the original builders at Izzo did likewise!

If the valve is adjustable it can be taken apart and cleaned, check the Teflon disc for damage or deformation, reassemble and check on reset. Likely a standard 1/4 BPP thread (measures about 1/2"). Use the hollow crush washer if you don't trust Teflon, which work as well...the hollow ones are easier to crush properly. This is all predicated on your pressure being below 1.5-1.8 bar depending on the valve.

TomC wrote:I don't know if my problem is the same or not, but on my unit I noticed tonight while it was coming up to temp that there was a steady, slow drip coming from the hot water tap.

No, your issue sounds like the compression washer in the hot water valve is worn/over-compressed. I would check with your vendor or CC, but I read 10 months ago (courtesy of same OP) that the washers are not available separately, in Izzo Duetto steam wand valve repair. Mine is at 10 months and counting, with no noticeable leakage or advancing of the shutoff point (indexed by a dot of tape at 12 o'clock on the knob). I suspect the trick to keeping these in good shape is to use the minimum torque that seals, which comes before you even feel resistance. If you crank it like your garden hose bib, it won't last. But unlike the hose bib, a 5-cent washer won't fix it.

TomC wrote:I imagine if the problem didn't go away, and I was plumbed in in the future, I'd have the risk of a big leak all over the place.

? If you plumb the drain, you have insurance, if you're only talking about the water wand drip. There's no risk of sudden, total failure; the drip will just slowly get worse.

TomC wrote:And if I leave it as is, I could run the reservoir dry.

Sure, if the drip is pretty bad. I'd be more worried about the water level in the steam boiler dropping low enough to expose the heating element, sometime after the reservoir stops feeding the boiler. I'd start by monitoring the tank when it's not in use, say, overnight, to see how much is lost. And you can always just leave the brew boiler on and shut off the steam boiler -- it will reheat in at most 8 minutes.

allon wrote:you can verify the setting an operation with an air compressor.

NEVER use compressed air unless you have very precise pressure control and volume regulation.