If you want it to be usable, then look for a minimum 18" sink size, or larger. Any smaller won't be able to fit in one of your stockpots or hold a colander for draining pasta or rinsing greens. The small 14" beverage sinks are exactly that: only useful in a bar situation. A 25" sink can usually fit in a cookie sheet or pizza pan and if you site it close to one end you'll have a lot of versatility for your prep.

???

I am going to have to respectfully disagree.

I don't have a prep sink (yet). But I do have an awful, old double kitchen sink that is shallow. both sides are 14in wide (15 front to back) and only 6 in deep.

VERY annoying for washing dishes etc. But perfectly usable for prep work.

How big are your stock pots? I regularly use my 8 qt stockpot and it fits fine. I have a 12 qt stock pot - I've never put it in the sink. I think it would fit, but that's not the way I use it.

I've paid attention to this question when it comes up on the forum and the majority of posters have mentioned "12" inches as the sweet spot of usability. Less than 12 can work, but not ideal. Larger than 12 inches is probably wonderful - but then you need to decide how much real estate you are willing to give up. With an island of 3x6ft, I'd not want to give up too much.

(for clean up sinks, it seems like anything at least 20inches wide will be sufficient. -- I am referring to the real basin size - not the outside measurement)

Mine is about 17.5" across, inside dimension. I would NOT, NOT want it any smaller. Even at this size, it sometimes seems small. If Silgranits were available in more size options, I would have gone slightly bigger. My colanders fit just fine. I wouldn't try to put a sheet pan in as that's not my style.

I have only had two very heavy prep/cook days though since we moved in mid-November, but I doubt my opinion will change.

An 18" sink is about 15" interior space. A 14" sink is about 11" which is too small for most colanders. I agree that an 18" is about as small as you'd want, and that larger is better if you have the room for it.

I'm in almost the same boat as you, bacin0. My island will be 54" x 39" (wish I had room for a 6' long island!) and I'm hesitant to give up a lot of counter to a prep sink but I also know one would be handy to have.

Because I intend to install mine at a corner with the faucet at an angle so it can be used from either the long or short side of the island, I'm leaning towards a round or square sink. Like this:

[traditional kitchen design[(https://www.houzz.com/photos/traditional-kitchen-ideas-phbr1-bp~t_709~s_2107) by san diego kitchen and bath Tina Kuhlmann

Blanco offers the Rondo, a 15.25" interior diameter round that requires a 21" cab for undermount installation and a 18" cab for drop-in installation. Interior dimensions seem like it would work but what about depth? It's only 6-5/8" deep. Undermounted with a 3cm counter, it would be 7-7/8" deep. Is that too shallow?

I also found a round sink from Franke, the Espirit, in stainless. It's interior diameter is 16 1/8", depth is 7 1/8". Required cab size is 21".

Franke also offers a round fire clay sink called Luna. It's interior diameter is 15 3/8", depth is 7 7/8".

Is there a minimum depth for a prep sink?

Hope you don't mind me tagging on to your thread, bacin0, but I figure you'd want to know this as well.

My island counter is 29"x70". I have the Blanco rondo (15" diameter bowl size) undermounted in an 18" wide cabinet with the inside edges of the cabinet eased down to the depth of the flange. Fits perfectly. There's 45" of counter on one side of the sink and 10" on the other. There's a garbage disposal in there (which I don't care about and rarely use) and a Tapmaster that I wouldn't be without. What helps is the cabinet is 27.5" deep (including doors) and the back of the cabinet appears to be finished with a door but is actually operating which makes it very easy to access the plumbing.

The sink size is exactly right for the island size. The round shape keeps it functional while minimizing the total size. The big colander fits fine - used it on Christmas for the lasagna. I don't see any reason to put a stock pot in the sink; I put it on the counter and fill it with the high arc pullout.

I wash small items there and the big things in the cleanup sink.

I've had my kitchen for over 5 years and not disappointed with my island. Go for it.

I have the Blanco Diamond Bar Sink in my 30" x 84" island and I love it. The outside dimension is 15"x15", and the inside dimension is 11.5"x12"x8" deep. I don't use the prep sink for washing dishes, but its perfect for washing veggies and fruits, and my strainer fits perfectly. I located it as close to the corner as I could, which is about 6" from each edge. If I were doing it all over again, I would do it exactly as it is. As I use my island for the vast majority of my prep work, and there is also seating, I didn't want to use more of the surface than I needed to. I did go with the pull down faucet, which I would also recommend. If I'm filling a pot larger than will fit in the sink, I simply place the pot on the counter and use the pull down.

My biggest stockpot (24qt, IIRC) fits in my square 14" prep sink with room to spare, not that I ever use it for pots, but I had to check it in reaction to the earlier posters who thought a prep sink had to be larger to be functional.
I use it for cleaning and peeling veg, so it has a huge disposal under. Also the faucet is tall and swings away to get the big pot it. And a 14" collander would be a pretty big one, I think.
Casey

The inside dimensions of my smaller sink is 13" across by 18" front to back by 10" deep. I find it is perfect for my needs. It was our only sink for the first couple of months before our main sink was hooked up. I didn't find it inhibited either prep or clean up.

Dh just resealed our counters the week before Christmas and I wasn't able to use the main sink for a couple of days. Again, I had no problem with just the small sink.

There are trade offs in kitchen design. For me, it wouldn't be worth maximizing the size of the smaller sink to accommodate everything in my kitchen when I have a perfectly good larger sink. Maximizing counter space for daily prep/cooling/staging space was much more important to me.

Putting in tall faucets with pull down faucets aided the usability of both of our sinks. I can put pots down on the counter next to either sink and fill them there.

In 6 1/2 years of using both of our sinks heavily, I've never once wished that our smaller sink was larger. There are a few tasks, i.e. cleaning large baking pans, cookie sheets and stove parts, that I much prefer doing in the large sink, but that's why I put in a 30" single bowl main sink. The only reason I can think I would find a second large sink useful would be if we used large items so much that I would want 2 people to be able to wash them at the same time at the 2 different sinks.

Mine is 17W x 14D and 9 inches deep from the countertop to the bottom of the sink. It's great but I really wouldn't want it any smaller. I'm not sure I've ever heard anyone complain their prep sink is too big (but it could happen!) but I've heard plenty of people complain their prep sink is too small.

Billy

We decided on a main sink that is a single bowl-- 30" wide and a prep sink that is about 14" wide interior x 16" x 10". This will make the prep sink slightly wider and deeper than 1 bowl in the 30" Kohler divided sink in the apartment we are staying at now. Big enough to fill our biggest pot, or clean a head of lettuce, but still not dominating the width of our prep space. Want a modern look but didn't want zero radius.

So settled on a pair of sinks from LeNova in their 1/2 radius collection.

http://www.lenovasinks.com/index.php?page=shop.browse&category_id=7&option=com_virtuemart&Itemid=5

Our cost was $316 for the prep and $468 for the main sink, plus tax (CA).

I knew I could count on this group for great suggestions. I never thought about using the tall pull down faucets on the island to accomodate larger pots. I am also going to measure my collander and appreciate the advice on the actual sink placement. Thanks to everyone for taking the time to respond to my post.

We did an 18" wide prep sink and I remember being shocked when it arrived in that it looked HUGE! As soon as we put it in, I was like "that's it?" I think the 18" sink is a good size to hold things without being too big.

During my kitchen Reno we were living in my big party room which has a bar with a round sink with an interior measurement of 16". I found that draining pasta was almost impossible without large splashes of boiling water. My new kitchen has a prep sink whose main purpose is draining things from the stove as the new stove is 8-10 feet from the main sink. I did a 21" x 19" prep sink over the objections of the kitchen designer who thought it was WAY too big. At our Xmas celebrations we had a second sink washing station which was a great surprise and cut the cleanup time in half!

I say go as big as you comfortably can.

Shortening clean up was exactly why we located our dw at our small, or prep, sink. Very little sink space is needed for any of the dishes that need to be scraped and/or rinsed. One person can be loading the dw while another is at the main sink dealing with hand washables. A third can be putting leftovers away and clearing tables.

Another thing to consider with the sink size is the cabinet size that is necessary. If you have plenty of storage, it may not matter. If you are trying to maximize every inch, then it should be considered along with the impact on counter space.