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Darkroom remodel


October 8th. Gutted the darkroom and spare bathroom. They share a common plumbing wall, so made sense to do both at once. Initially I’d just intended to replace the darkroom sink. Talk about scope creep.


Woof. This surround is about as thick as a magazine cover and was contact-cemented to the wall. As crappy as the original kitchen, bath, doors and carpet were in this house, at least it’s square, plumb, and level. But note the odd location of the tub drain- centered, tight at the back wall. This really complicated finding a new shower pan to fit- the joist layout means I’ll have to cut and header-off a joist to put in a standard 30″ x 60″ pan with center drain.


About as wide a view of my 10×10 darkroom as my camera will get. But I wanted to get a shot of the old setup in all its shame before removing the sink, fixtures and flooring. The pipe wrap is an elbow cushion- I’d rimmed the old sink with aluminum angle. Hard to see, but the floor was blue and white VCT tiles in a checkerboard pattern, with vinyl cove base. The cabinet in the foreground was a remnant from a old kitchen remodel, and I made a presto 2×4 table to span the rest of the sink space. I found a good new use for them-out in the garage supporting the new sink until I can install it.
Plumbing crime. Originally I’d stolen the supply from the tub I thought we’d never use (sorry guests), and extended the tub’s waste line to put in this drain. Surprisingly, this setup never leaked once in 12 years. I didn’t want to add a new vent stack for the darkroom, so used a Redi-Vent. This worked well so I’ll use one again, but this time I’ll use a proper horizontal wye instead of this sanitary tee.


Redid the floor with resilient plank vinyl. It’s a floating floor, the edges overlap and seal, so only had to scrape and mop the VCT tile and lay the new floor right over. I used similar flooring in the kitchen remodel 6 years again and it’s held up really well. I cleaned up the pluming a little by installing a couple of Pex ball valves at the plate line (to be accessible though a soon-to-be installed cabinet). These shut offs will allow repairs to either the shower or darkroom mixers. Also extended the waste line so it doesn’t take up so much cabinet space. The ugly mud patch was from moving an electrical outlet way back when I first converted this bedroom to a darkroom. I had to move it back to the original position.  It’s be covered by the cabinet, so just turned this into a junction box and ran wire for a new outlet at the timer shelf way above. I’d like to murder whoever textured the walls in this house. Not so much orange peel as stucco.


October 15th. The 2×4 sink base was wrapped in heavy kraft paper to protect the floor in case I convert this back to a bedroom someday. Eventually the base will be wrapped with baseboards. I sheet-rocked over the waste line but left the bay with shut-off valves open. Had to relocate this electrical outlet on the left as well. At least the floor was where it needed to be- dead level side to side and front to back.


I made some simple base cabinets out of melamine yesterday. Banded the exposed edges, and used 1/4 plywood for the backs. The cabinets are deeper and shorter than standard, 28″deep x 29″ tall (34″ tall including the base and substrate), each one is 27 1/2″ wide so I can make all 6 doors the same size. The sink substrate is doubled-up plywood with staggered laps, 1 1/2″ thick, the outside edges banded with black Formica. The openings will allow me to shim the sink bottom along the kerf lines to keep it from flexing. I’ll laminate the cabinet doors and backsplash with Formica as well. The substrate is 34″ off the ground, which puts the rim of the sink at 40″ and the sink bottom at 35″. Will try to finish up the darkroom side of this project next weekend.

October 18th- put the sink and DWV in last night. Just barely fits with the door open.



Drywall is slightly out of square. Rather than scribe the epoxy-covered rim to fit, I shimmed it and will fill the small gaps with silicone. The backsplash thickness will cover the gaps too. I decided not to cover the aprons, at least for now.


Drain was seated in plumber’s putty on the wet side to seal the flange. 1 1/2″ tailpiece off the sink, but the rest of the drain is 2″.  Have just enough headroom to replace the Redi-vent if needed.


Shimmed the bottom of the sink at each cabinet to keep flex to a minimum.

October 28. Couldn’t work on this last weekend, when I was in the crawlspace moving the tub waste line I noticed the foundation needed some emergency work, so had to spend the weekend shoring that up.


Back-splash is 1/2″ plywood, edged and faced in Formica, all seams were caulked with silicone. I’ll probably add a rail above the backsplash with hooks for things like squeegees and print tongs.



Mixer is a bare bones arrangement of an in-line thermometer and 2 globe valves, which will stay set at 68° On the left is a branch hot water line that bypasses the mixers, for cleaning up without having to change the tempered water. This configuration isn’t ideal- it should have check valves on each side to prevent the cold water from flowing into the hot side and vice versa. I may end up replacing the 2 globe valves with a single shower valve that has internal checks. [Did so, update below.] I used 1/2″ CPVC pipe, and threaded unions so it can be disconnected at the wall if I decide to reconfigure it. The CPVC is so cheap and easy that I figure I can just cut it free if i change it, but if I do I don’t want to have to chase it back into the wall. The thermometer has a 1/2″ NPT collar that threads into a stainless steel cross, the 2″ probe from the thermometer reaches almost to the opposite end of the cross.


An outlet for the hot water, and two for cold- one for the print washer and another for mixing up solutions. I used drop ear 90°s for the valve faucets and lots of pipe support to keep stress low on the pipes. Still need to make a standoff block to secure the lines above the mixer. I like CPVC, used it on the last plumbing setup and it worked really well, 12 years without a failure or even a leak. I thought about PVC Schedule 40 but even the 1/2″ fittings are really bulky, and the temp range for the pipe is less that CPVC.
The two gate valves  (black handles) are useless- I had some unused ones lying around and thought I would save some money, but they already drip when completely closed off. I’ll replace these with ball valves. I like the globe valves for the mixer and the print washer outlet, they’re better at regulating flow. I decided not to put a water filter back in- I had one but the water quality here is so good that I’ve been going without a filter installed in the system for many years. Quick disconnect hoses that attach to the outlets will have anti-siphon valves on them.


The lines at right are for the darkroom. I dry-fit the mixer fitting to find the right layout for the stub-outs, then mounted some drop ear Pex fittings to a 2×4 block (top right), made the Pex supply connections, then threaded the nipples onto the drop ears, then drilled through the backsplash. I then set the block so that the nipples would stick through the back-splash with enough room for the escutcheons and the union threads.
76 plumbing joints between the CPVC on the darkroom side and Pex on the bathroom side. I was a little nervous charging the lines. The Pex is easy enough with a good crimping tool, and the CPVC slip fittings are pretty foolproof too. But the threaded CPVC fittings are tricky- they say not to over-tighten, just 1.5 turns past ‘finger-tight’. I used ‘Universal’ thread sealant (for both plastic and metal pipes) and laid out the parts to avoid using any female plastic fittings, only plastic MIP into brass/ stainless steel FIP. There’s little change of splitting a metal female fitting with a plastic male thread, but apparently the female CPVC threaded fittings split easily if over-tightened.

November 5th. I redid the mixer, adding a tempering valve with internal checks so there’s no cross flow from cold to hot and vice versa.  Also adapted the swivel spigots and print washer hoses from my old setup to fit the new quick-releases at each supply valve.

‘Anti-Sweat’ valve- actually these are intended for toilets, to add a little hot water to keep the toilet tank from sweating. It has 1/2″ nominal compression fittings (5/8″ OD), which is makes it easier to take apart if needed. There’s an adjustment screw on the hot side to dial in the temperature, from closed to fully open. I’ll add a thumb wheel to the screw to make it easier to adjust. This valve isn’t perfect for tempering, but it’s only about $20. I liked the compression fittings on the anti-sweat valve so much I replaced all the CPVC MIP fittings at the gate valves fittings with them, allowing brass-to-brass thread connections. The CPVC threads are treacherous- too loose they leak, too tight they deform and leak. Hard to find the sweet spot, regardless of the sealant used. The compression fittings are nice because they can be tightened when installed without turning the entire valve body, so if I need to swap out valves down the road it will be much easier.
Securing the whole thing took some head-scratching due to the distance of the plumbing from the backsplash. I made a few standoffs out of aluminum and attached them to a 1/4″ aluminum plate, painted them black, and modified a burly stainless steel drawer pull to hold the tempering valve securely to the plate.


I was asked how I keep things sitting level in a sink with compound slopes- I use composite shims that won’t rot or swell for stationary fixtures like print washers, and build in leveling feet for things that move around, like this Jobo motor base above. I may eventually make tapering duck boards.

Update 10/2018

Two years along things are holding together well. The ‘anti-sweat’ tempering valve isn’t ideal as a thermostatic mixer, the temperature does drift depending on flow rate. A thumb nut installed on the adjustment screw makes it easy to tweak, but a pressure-balanced valve would work much better.

I had a leak- One compression fitting failed on the upstream side of the cold water at the valve, but that was probably due to a failure of the house’s PRV. The water pressure in the house had crept up to 110 psi. Even so I replaced the tempering valve connection to the cold supply with a braided flex line. I should have used this from the beginning, much easier to connect than all those CPVC elbows and compression rings.

Sink is doing well. One curiosity- ‘Indicator’ stop bath stains the epoxy coating. The surface must be fairly alkaline because undiluted stop leaves a cyan stain as soon as it hits the deck, even cured epoxy seems to activate the dye. But the stains buff out easily with some synthetic steel wool.