"Alex" wrote

add a small bar with running water for making drinks, washing hands,
etc. This new room will be a good distance from the kitchen or any
water sources in the house, plus we have a concrete foundation.

Just curious, would it be feasible or recommendable to run flexable
hose of some sort through the attic to this sink from the kitchen or
someplace else in the house? I've seen this done with copper tubing

Nope. Sprink a leak and you will cause massive ceiling damage. You have
water pressure issues from the main line and may have temperature problems
depending on where you are.

As for drainage, since this sink won't be used very much, my thought
is to drain it into the yard as we have a planter just outside where
the sink will be located.

Make sure that's legal in your area (some are, some are not).

I have a possible easier answer if this is really a low use water need.

Did you consider just using a sort of water cooler type device with a small
tap over a 'sink'? This could be as simple as one of the bigger (5g or so)
bottles that sits on a ledge over the sink with a tap at the bottom you
twist to let out some water, or the bigger bottles you might see in an
office building.

It may not be as fancy as you were thinking of, and yes you have to refill
the bottles (can use tap water if you want), but I have a neighbor with a
system like that in his back shed.

Ths is what he did: The shed isnt attached to the house and he uses it for
car projects and such. He has electricity but no water. Because he is
often cleaning car grease and such off his hands, he has one big bottle in a
top cabinet with a spigot that sticks out from a cabinet above, and this is
over a small sink with a cabinet below. Inside the cabinet below, is
another bigger bottle (top cut mostly off) to catch it all. He just dunks a
piece of cutoff garden hose in the bottom one, tucks a thumb over one end to
hold the water in and puts that end in a bucket to let it drain to the
bucket. He takes the bucket to inside (our area doesnt allow greywater
dumping and his had solvents for grease anyways) and dumps it to the city
sewer line.

Because he is older and can not lift much, the bucket is smaller and takes
about 3 drainings to get the lower larger bottle empty. The upper 'feed'
bottle is deliberately smaller so he never accidently overloads the lower
'drain' one. When the top one is near empty, he just drains the lower one,
then refills the top one. In his case, refills with an exterior hose which
is about 10 feet away on the back of his house.

Because he has nice little cabinets over the top bottle and bottom one (a
bathroom sink enclosure at bottom, a matching bathroom wall cabinet at top
with a hole for the spigot), it actually looks very nice. I am not sure
exacly, but the top feed bottle looks like 5gallons, and the bottom one
might have been 10 before he cut the top down a bit to make putting the hose
in easier. It still holds more than 5G.

If there are no 'grey water' resitrctions where you are, you could just run
a hose from the bottom of the sink to outside as you were thinking, and
dispense with the need to empty a 'drain bucket'.

Anything useful in that for your needs?

If it also helps, he was worried about the weight of the 'feed bottle' on
top so the cabinet was placed right between studs and reinforced with more
2x4 'H' ' 'jointed' between. He probably over did the bracing needed but it
only took about 1/2 hour to add the extra wood to make sure. Hope I used
the right terms there for the 'H' joint.

| |
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|-------|
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|-------|
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S I N K TOP
(BOTTOM CABINET)

If I did that simple drawing right, you'll see 2 studs, with 2 crossbars
added then a 2x4
running between the studs butted up to the 2 crossbars. The 2x4 between the
studs, runs to the cement floor behind the sink cabinet.

Grin, even if this wasnt what 'you' needed, it may help another and was fun
to type. I think my neighbor quite inventive there!