Whale wrote: As I wrote the Vivaldi, and pretty much all other rotary pump machine, have a by-pass conduit that one can adjust to control pressure. This is a regulator! I do not think that having another regulator upstream would increase the stability of the group pressure in a significant way. This is just an opinion that I have not experimented.

Some machines have pumps with balanced by-pass valves, in which case you are correct. Others do not (mine for example). I was well aware of the different types when I replied, which is why I specified that the pressure regulator is needed if you have a pump that just "adds pressure".

I'm assuming that the machine asked about has a balanced bypass type.

Many Vivaldi owners have posted on the S1 forum about having to readjust group pressure after receiving their machine as CC sets them with a line pressure of 30 PSI. If your line pressure is higher or lower your group pressure changes. Play with your line pressure & see for yourself.

SwingT wrote: Having said that - I finally got my S1V2 tasting a lot more like my Cremina (which I prefer) and happened to look under the counter and see the gauge ( which I got from Chris at the same time) while pulling a shot - was at 22 psi, which was a surprise - I last set it at around 35. The incoming pressure changed and/or the larger pressure regulator shifted it's band of operation - anyhow something shifted.

22 lbs is lower than most will recommend - but sure tastes nice to me - obviously, individual tastes and preferences can be markedly different.

Even so, works beautifully for me.

Your group pressure is probably closer to 8b or less as a result which is why it tastes closer to the Cremina.

Don't get that crappy plastic regulator - get a good brass one. Costs are the same and you won't get a flood from a cracked body like I did.

Apart from the original question, if I fill my boiler (to the correct level), will the machine work with no inlet pressure? I am waiting on a regulator would really like to know it the machine actually works:(
Re: Brass regulator, where can I get one? I looked and all I could find were 1" and 3/4" designed for main line use.

There are a heck of a lot of us using the plastic regulator that CC sells & Ben's is the first report I've seen of cracking. Mine is 3 years old with no issues & as long as it doesn't freeze or you don't over tighten a fitting I don't see why it would crack. Brass units are out there but usually cost around $100 although there may be better deals available. Do a search under Watts brass pressure regulator & you will see several 3/8" options.

DigitalDave wrote: ... (asked some questions)

You could heat up your boiler if you fill it with water first. But you can't pull a shot or anything useful without the pump running. A rotary pump won't be happy without positive inlet pressure in contrast to a vibe pump which will run fine from a reservoir. If you must & only as a temporary setup, use a reservoir elevated above the level of the pump. Use the deepest container you can manage, so that you have some nominal water pressure. But why can't you source a water pressure regulator locally? Or if you mail ordered one to take advantage of a better price, then wait until it arrives.

Brass is more rugged, but also double the price. Most people use plastic pressure regulators and it would be rare to have one crack unless you impact it with something or let it freeze. You can't have looked very hard for 3/8" brass regulators if you didn't find any. Google pulls up a million sources e.g. Grainger.com, etc. Not to mention just about any local plumber's supply & probably even your local Ace Hardware or equivalent.

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wookie wrote:And a rotary pump is not going to be happy without positive inlet pressure in contrast to a vibe pump which will run fine from a reservoir.

Maybe, maybe not. See Do most plumb-in machines require external pressure? and notably Can a rotary pump suck up from a bucket? for background information:

Chris Nachtrieb wrote:Every time you run the tank dry, even for a short time, or have to prime the pump because it loses prime, you are doing damage to it. If you insist on running it that way, at least put a good check valve in line so as not to lose prime. Bottom line, a pump run this way versus the way it was designed to run is much more likely to wear out sooner than it should.

I offer some other caveats here.

Fair enough, Dan. I stand by my comments though. It's not so much a matter that a rotary pump won't work without positive inlet pressure as it is bad practice that can shorten a pumps life.

My main concern would be cavitation, particularly with common inlet line sizes which would be inadequate for very low inlet pressures. And should you run a reservoir dry, the pump will lose prime entirely. Either case is stressful to the pump.

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There are regulators, and then there are regulators. There's no such thing, to my knowledge, as a regulator that holds output pressure constant provided inlet pressure is greater than or equal to line pressure, short of an active regulator comprised of a choke with a process controller (and now we're talking about a regulator that costs probably more than your espresso machine!). Mechanical, passive regulators produce an output pressure that varies to some degree with flow rate and inlet pressure. The interesting question when considering such a regulator is how sensitive output pressure is to variations in flow and inlet pressure. For espresso applications, flow rate variations are a pretty small concern for the most part: your flow rate when it matters (during a shot) is going to be very low and very consistent. Variations in inlet pressure are likely much more of a concern (what happens to your water pressure when you flush a toilet, when you run the kitchen sink faucet next to the machine, when the washing machine is filling, etc.). Cheap regulators can have near-direct variations of output pressure with inlet pressure (fixed flow), whereas nicer ones will see sharply less variation (e.g., for a 15 psi drop in line pressure, you will see a <1 psi increase in output pressure, assuming inlet pressure hasn't dropped below output pressure).

I'm far, far from an expert in regulators (EricS is probably the man to ask real questions to), but my experience with the black $30 regulator from ChrisCoffee is that it is rather sensitive to inlet pressure variation. I believe that the brass Watts regulators with real-big diaphragms are much more robust in terms of being less sensitive to line pressure variation. This isn't really an issue in most cases, and I'd have no problem recommending the little black regulator. Mine lasted me at least 3 years before I retired it, not because it wasn't working but because I got my hands on a ridiculous ~$300 Swagelok regulator for next to nothing.

DigitalDave wrote:Apart from the original question, if I fill my boiler (to the correct level), will the machine work with no inlet pressure? I am waiting on a regulator would really like to know it the machine actually works:(
Re: Brass regulator, where can I get one? I looked and all I could find were 1" and 3/4" designed for main line use.

If you do want a good brass regulator, you can get Watts regulators on Drillpot.com. One like this will run you about $50. You will need to get adaptors to go from 1/4" Female NPT to whatever you're using to hook your machine up to the water supply, and you'll also probably want a 1/4" Male NPT water pressure gauge to attach to the regulator so you know your outlet pressure. Check the site for a lot of other options. You can get different inlet/outlet sizes, different output ratings (the one I linked is max 300psi input, 3-50psi output), etc.