This might be a dumb question, but googling it just points me towards high flow tankless RO systems which isn't what I'm after.

What I'm wondering is, is it viable to run a tank RO system without the tank in a low-volume application such as a dedicated line for coffee?

After asking about my water report here it was suggested that RO was the way to go. Ordered these two items for it:
https://www.amazon.com/gp/product/B00I0ZGOZM
https://www.amazon.com/dp/B01MZARUXV

Plan is to mount these along the rafters in my basement. I was going to put a T splitter at the line that splits off the main to feed my fridge, and from there it's about 15 feet or so to get to where it needs to go. This line will then feed a pot-filler style faucet I'm mounting into my backsplash in the kitchen above, with a line connected to it where it's sprayer is supposed to be to feed the Synchronika and then I'll have the faucet to fill the La Pav and the drip machine.

Given the low volume/usage per day (I typically only pull a couple doubles in the morning and maybe one or two more later in the day), is the RO tank really needed? I'd prefer to avoid trying to mount it up in the rafters, but if I need it for system pressure or something then so be it. I don't know if it's purely for storage to have on-demand water or if it serves a more critical purpose.

The system on the first link is 50 gal/day. If I did the math properly, that's around 2 mL/s. That is not fast enough to keep up with even traditional espresso flow rates. Even if it were, the accumulator plays an important role in allowing a regulator to work.

If space is an issue, there are smaller accumulators available.

Maybe I'm missing something here but I don't need it to keep up with espresso for rates directly, as far as I'm thinking. It only needs to be able to refill the Synchronika's boilers between one morning and the next.

Or are you saying that without the tank using the faucet to very occasionally fill the other machines wouldn't work?

It's not so much that space is an issue, just that mounting the tank is a bit more of a pain than mounting just the filters. If I need the tank in there then so be it

The system in your link includes an accumulator tank. It should work fine. I have the same set-up here, but didn't add a remineralization cartridge. I used to have a blending valve, to blend back in some city water, but our water is so hard that the output of the RO system is high enough most of the year (depends on which wells the town has online). My system feeds a standard PEX line that parallels the hot and cold lines in the basement. It Tees off to drinking water spigots in the kitchen, coffee bar and the bathrooms. You do need the accumulator tank, though; I was a bit puzzled by your tankless reference. Without the accumulator, the water output from an RO system such as yours and mine is a tiny trickle, not enough to feed an espresso machine.

PS if you plumb it to the espresso machine, as opposed to using the RO water to fill the reservoir in your machine, don't forget to put in a pressure regulator. Although the flow from an RO is rather low, even with PEX lines, the initial pressure is as high as the incoming line pressure.

mcantar wrote:Maybe I'm missing something here but I don't need it to keep up with espresso for rates directly, as far as I'm thinking. It only needs to be able to refill the Synchronika's boilers between one morning and the next.

That's not really how it works. The tanks fill only when the machine is on via the internal pump, on demand from the water level sensors. If you make more than a couple of espressos in a session, the pump will come on. You need the accumulator. It works exactly the same as it would if you plumbed to your regular water mains.

Listen to Maurice and Jeff - you need that accumulator. When the Synchronica's rotary pump does an autofill, or when you start a brew, the feeble ~100 ml/min flow out of that 50 gpd RO membrane will not be sufficient, and the pump may cavitate and suffer damage.

P.S.
If it were me I'd just use the APEC calcite filter with that system and not that Oceanic alkaline. The APEC FI-PHPLUS-QC is simple calcite, which is dependable, predictable, no nonsense. It's also manufactured and tested per NSF standards for materials and construction. The Oceanic costs more and is not well specified as to what it contains (looks like some snake oil in there) and how it performs.

Thanks for the info all! And good point about the pump cavitation.

I just went and cancelled the Oceanic filter and ordered the APEC one. That'll work out better anyway as now it'll all arrive at the same time, the Oceanic had slow shipping.