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Thread: Darkroom Sink Slope & Drain?

  1. #1
    Jeffery Dale Welker
    Join Date
    Sep 2006
    Mesa, Arizona

    Darkroom Sink Slope & Drain?

    I'm preparing to build a sink for my darkroom. It will be 8'x30" and constructed out of 3/4" birch plywood.

    I would appreciate comments about the amount of "slope" I should be designing into the floor/bottom of the sink so it can drain properly. I'd like to go with the minimum slope possible so my trays aren't cattywampus. I'm also wondering if you have your drain is "in sump". In other words, at the absolute low point of the sink so all liquids runs directly to the drain? In studying various plywood sinks online, I see where some drains are located in a corner. Some centered in the middle of the sink. Some are centered at on the end of the sink. Very few look like they are actually "in sump". It appears at least some water/chemistry needs to be squeegeed to the drain. While I realize the drain location is dictated by where the sewer pipes are in the wall, I am mainly interested in what works best. For my darkroom, the drain will be located at one end to facilitate connection to the existing plumbing system.

    I'm not trying to overthink the room or make this too complicated, but birch plywood is expensive and I'd like to get this right on the first try.

    All comments and suggestions are appreciated. Please share photos of your sink if reasonably possible.
    "I have this feeling of walking around for days with the wind knocked out of me." - Jim Harrison

  2. #2

    Join Date
    Jun 2001
    North of Chicago

    Re: Darkroom Sink Slope & Drain?

    I've built several sinks and always used about 1/4 inch per foot slope with the drain in the lowest corner. They worked fine.

    Richard Wasserman

  3. #3
    Jim Jones's Avatar
    Join Date
    Aug 2006
    Chillicothe Missouri USA

    Re: Darkroom Sink Slope & Drain?

    Salmo -- Having the sink's drain near available plumbing is the logical way to go. As for the slope of the sink, rather than design that perfectly, just build it with the often recommended 1/4 inch slope, and adjust it later by shimming the sink if desired. Practical construction often beats tedious engineering.

  4. #4
    Tin Can's Avatar
    Join Date
    Dec 2011

    Re: Darkroom Sink Slope & Drain?

    I prefer 'in sump' aka lowest corner in back wall side at fixer end

    I use 1.5" PVC and have connected 3 drains in 3 sinks in my 2 real DR all with 'traps'

    I really like PEX for pressure water and use brass valves all over

    I made a mistake by cheaping out with a bit of iron pipe fittings for the Hass Temp control

    Then I bought the heavyduty PEX Crimper, it saves money

    My pet peeve is too many 90's, I like to gently curve PEX

    I have done a lot of industrial plumbing for 30 years
    Tin Can

  5. #5

    Join Date
    Sep 1998
    Oregon now (formerly Austria)

    Re: Darkroom Sink Slope & Drain?

    Some random thoughts:

    I built a 10-foot sink some years back. I used the 1/4-inch-per-foot rule and it works well. I placed my drain in the center rear of the sink so as not to have too much height difference from side-to-side. Make sure to slope the sink bottom not only from side-to-side, but also front-to-back. If you're placing the drain in a back corner, then that should be the lowest point. If in the center, then center back should be lower than center front.

    I made an earlier sink that had a drain in the right front corner. That worked well too, but it was a smaller sink.

    It's easier sloping a sink with the drain in one corner than in the center. Simply divide the height difference you need from one end to the other and subtract half of that from the leg under the drain and add the other half to the diagonally-opposite leg.

    My present sink drains well, but when I'm not printing for a while, I'll squeegee it out and wipe it dry. I used marine plywood for the sink bottom and faired the corners with marine epoxy and sanded smooth, then primed and painted with marine topside paint. The advantage for me is that I can repaint small areas or the entire thing easily; just wet sand, dry, wipe down and paint. The marine paint levels out very nicely.

    I made a double-thick front splash and rounded the top so now I have a comfortable place to rest my arms when processing (especially nice when shuffling film in trays in the dark - I found the right height for the front splash so I can rest my arms on it and reach the trays).

    Had I had room, I'd have made a sink-size sump in one end of the larger sink with a dedicated faucet for dumping trays, clean-up, filling jugs, etc. Maybe that's something you wish to consider. As it is, I use a large funnel stuck in the sink drain to dump trays into (I hate just turning them over in the sink and then having to clean the entire 10-feet of sink later).

    I made the sink splash guards all the same height. I then had a 10-foot x 42-inch countertop made, which I cut into sections, reinforced and shimmed so I can lay them out over the sink, resting on the tops of the splash guards to convert the sink to a 10-foot-long work area that I use for print mounting, framing, etc.

    To that end, I have a separate 15-amp circuit (GFI, of course) with two sets of four outlets along the wall in back of the sink. I can use this for timers, etc., but use it mostly for my dry-mounting presses, tacking irons, etc., when mounting prints. I can also get my 72-inch mat cutter onto the counter and use the surface for cutting mats as well.

    Hope this helps a little,


  6. #6

    Join Date
    Nov 2017

    Re: Darkroom Sink Slope & Drain?

    if you want your trays and whatever else level, you could just add a little level strip around the sides of the sink to support wire mesh shelving or those plastic grids they put on ceiling light panels.

  7. #7

    Join Date
    Aug 2017

    Re: Darkroom Sink Slope & Drain?

    I have my plywood sink flowing from front to back. Have a 4" trough at the back which is just a strip of ply fixed under the main ply so is the depth of the thicknes of ply. Install slats on the sink so trays aren't sitting directly on sink so moisture doesn't build up when trays are left sitting. Put a sink plug and waste at bottom end of trough. Paint the whole lot with pond paint.
    Fall should be around 1:60 as previously mentioned.

  8. #8
    Eric Woodbury
    Join Date
    Dec 2003

    Re: Darkroom Sink Slope & Drain?

    My sink is that size. I built mine flat and level and adjusted with blocks under the legs. It's about 1/8" per foot and it's plenty.

    With a router, cut a relief for your drain flange so it is flush with the surface. Water seal before you place the drain stem and again with extra goop when you install it.

  9. #9

    Join Date
    Dec 2014
    Iowa City, Iowa

    Re: Darkroom Sink Slope & Drain?

    I have 2 lovely sinks that I have scrounged over the last 30 years. One is a Kreonite fiberglass litho sink 8 '. The neatest thing is a trough in the back to empty trays and tanks. Still has a drain for the main sink too, drains are in the center back. My other sink is Arkay SS 10' drain is in far right rear corner.

    I always squeegee the SS sink dry. It drains quite well, just nice to squeegee, especially if you make a nice wood sink. Kodak had a formula for a stain for wood sinks and benches but modern coatings are bulletproof.

  10. #10
    Pastafarian supremo Rick A's Avatar
    Join Date
    Feb 2010
    Laurel Highlands, Pa., USA

    Re: Darkroom Sink Slope & Drain?

    Here's a little something to think about when building a sink. Sanitary sewer fall per run is figured to keep "solid waste" moving. Everyone thinks they must follow the 1/4 inch fall
    per foot of run is necessary for their trough, not so, you can get away with as little as 1/16 inch per foot. Remember, you are not trying to flush a (you know what) down the drain.
    Rick Allen

    Argentum Aevum

    practicing Pastafarian

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