Darkroom Sink Drainage/Slope Question

[Richard Wasserman]

I am in the process of designing my new darkroom and it looks like I will have a 15 foot sink. I know that the usual slope for proper drainage is 1/4 inch per foot—this works out to 3 3/4 inches over 15'. Do I really need this much slope? It seems like a lot, but of course it is a LONG sink. And yes, the drain needs to be at the end, not the middle. I can work with it if I need to, but just thought I'd ask for clarification. Thanks!

[Jac@stafford.net]

No, you do not need that much slope for a 15' sink.

To suit yourself, you might consider having supports (legs) of the sink height-adjustable. There many ways to accomplish this from using wedges to mechanical adjusters. Both are widely available, but I use the mechanical.

[Richard Wasserman]

Thanks Jac, that's the answer I was hoping for! Less slope should make my life a bit easier.

BTW, I sent you a PM.

[AtlantaTerry]

I have built many darkroom sinks using marine plywood coated with Fiberglas epoxy.

My estimation is that you would be OK with a total of 1/4" drop over the 15 feet.

[ROL]

My present sink (http://www.rangeoflightphotography.com/pages/a-darkroom-portrait#wetside) is longer than yours. I used the ¼"/foot rule, lengthwise and to the rear, where the drain sits in the corner. Large amounts of water and dumped tray chemicals drain fairly well (along the rear) from the not-as-smooth-as-I'd-like-it-to-be gelcoat finish. I end up chasing small amounts of chemicals (i.e., pyro, selenium toner splashes) from near the far reaches of the sink down to the drain with my overhead sprayers all the time. I use restaurant style drain mats to allow drainage underneath, and to attempt very approximate leveling for, processing trays.

[Jess C]

I've always used 1"x3/4" wood strips glued and nailed on the interior side panels to create the proper slope from one end to the other. The bottom panel is cut to fit and dropped in and secured with glue and a trim nail gun from outside of the side panels. I also used epoxy for the water proof finish with all gaps and joints sealed with a good quality caulk prior to applying the finish.

A squeegee is a good thing to use to direct any amount of standing water that may occur to the drain.

[John Olsen]

I built a lot of sinks with a careful 1/4" per foot slope then realized this was a little obsessive. I just checked with my level, and my current sink has a 1/4" slope over a 30" distance. I'm just building them now with a flat bottom and shimming up one end to give that small slope. My local lumberyards never have marine plywood; I just use what they have a paint it with Varathane. Every few years I sand it a bit and recoat it. My main sink is 20 years old and has been dragged around thousands of miles in three states. Don't make the sink construction a major task - just slam it together and get going with your photography.

P.S. The 1/4" rule is to make toilet solids go down drains. If you don't poop in your sink, you'll be OK.

[gleaf]

It all depends on how much flow you need down the slope. Less slope, Less 'head' to move the fluids. If you have no issue with speed then little slope is no issue.
If you expect to dump a tray and have it run off quickly then otherwise.
I would allow for some flexibility at the drain coupling and have jacking screws to lift the appropriate legs. Start level and lift it until it works for you.
Flat Roofs are about 1/2 inch per foot to dump very large rain loads. So 1/4" per foot will move a lot of water down hill. Happy is the medium that works.

[KennyMark]

P.S. The 1/4" rule is to make toilet solids go down drains.

This is true. My plumber told me that since the advent of the water-saver toilets, they typically make the waste pipes slope 1/8" per foot so the water doesn't leave the solids behind in the pipe.

[Richard Wasserman]

This is all very interesting, thanks. It sounds as if 1/8" per foot slope will work well. I will build the sink with this slope and if there is a problem with drainage I'll simply increase it. A 2" difference in height over the 15 foot length of the sink will be much easier to deal with than the 4" I was initially planning on.

[Rick A]

The 1/4"/ft rule is so solid waste can move through a sanitary pipe, you can get away with far less slope for liquids.