Calibrate the faucet on an Arkay Processing Sink

[jaymus]

I picked up a nice little Arkay Processing sink, which I've been using as a general purpose sink for developing film. The built in thermometer and faucet works great for color. I can get my washes right at 100 degrees without fiddling with hot and cold faucets.

In the picture, the faucet in the middle turns on the water on and mixes the hot and cold (I also included a closeup shot). The more you turn it, the hotter it gets. The only issue is that the mix is off. Turning it on the minimum amount gets me at 75 degrees, which it too hot for b&w.

There's gotta be a way to calibrate this thing. I haven't found any information online, I'm hoping someone here might know the answer.

Thank you in advance!

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160800

[Christopher Barrett]

Firstly, are you sure your cold water supply is under 75? Its not in a lot of places.

[jaymus]

Yep, it's colder. The sink also has a normal faucet with hot/cold and the straight cold is at 62 degrees. So it's mixing quite a bit of hot water right off the bat.

[jaymus]

The back of the sink doesn't have any apparent mechanism or valve for controlling the mix. It's gotta be done by removing the faucet itself, I'm just not that experienced with it.

[jaymus]

http://christopherbarrett.net

Gorgeous site BTW

[faberryman]

Are there shut-off valves on the hot and cold water pipes where they come out of the wall. If so, you could close down the hot water pipe a bit so the balance between hot and cold veered more toward the cold.

[Richard Wasserman]

You might ask Arkay— http://www.khbphotografix.com/arkay/

[Leigh]

Check your water pressure. Household water is supposed to be 60 psi max.

I had to install a full-service pressure regulator since mine was about 90 psi.

- Leigh

[ic-racer]

Some Arkay branded equipment used Watts Industries Co. mixing valves. Your mixing valve may be similar to the one in the Arkay CP-1000. I was able to get every service part, gasket, o-ring, etc. for mine through Watts Industries. In fact I just replaced the leaky check valve in mine last month.

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[Leigh]

Another thought...

Given that there are valves controlling the water into the darkroom, are they both fully open?
If the cold water valve is slightly closed it will limit the amount of same the temperature control can pass.

And you can close the hot water valve partially to limit how much can be presented to the temperature valve.

- Leigh

[Bruce Barlow]

If your mixing valve is at all similar to the one on my shower (which is similar to the one in my darkroom), there's an adjustment that you can make that adjusts the temperature of the water coming out. It looks like it is similar, from the picture.

There are about a billion videos on YouTube that take you through temperature adjustment of shower valves, because different brands and models of valves are...different. In my case, I got the general idea, tried what I thought would work on mine (one has a 50-50 chance of getting it right the first time), and got lucky. Now my shower is hot enough, where it wasn't before.

Afterwards, I felt smug with my accomplishment. My darkroom valve was installed by a competent plumber, rather than the one that installed my shower valve, so it is fine, and locks into 70 degrees every time.

Give it a try. You can make it work.

[jaymus]

Thank you, all! I'm going to try a couple of things. I'll report back.

[HMG]

I don't know if your valve is a pressure-balancing valve, but if it is...

I remember reading on a plumbing forum that pressure balancing valves rely on a device that, if it fails, can allow hot water to enter the cold line and vice versa. If so, you might need a new cartridge.

[Robert Bowring]

I second the idea of replacing the cartridge. My mixing valve was doing the same thing. I pulled the old cartridge out and everything looked fine. I bought a new cartridge and compared it to the old one and could not see any difference at all. I put the new cartridge in and it works fine now. Still can't figure what was wrong with the old one. It was a cheap and easy fix.

[Leigh]

I bought a new cartridge and compared it to the old one and could not see any difference at all.
Hi Robert,

The filter fixtures I've seen feed the water into the center and collect it around the periphery.
So any contamination and gunk will collect from the middle outward.

If you can see it on the outer surface, the filter is indeed VERY dirty.

- Leigh

[HMG]

Hi Robert,

The filter fixtures I've seen feed the water into the center and collect it around the periphery.
So any contamination and gunk will collect from the middle outward.

If you can see it on the outer surface, the filter is indeed VERY dirty.

- Leigh

Leigh, I think you're referring to a filter cartridge, and I'm pretty sure you're correct about the direction of flow. But I (and Robert I believe) was talking about the faucet cartridge that controls hot and cold.

[Leigh]

Yes, my comment was about the contaminant filters for particle sizes around 5 microns*.
These are large replaceable units, about 10" long and 4" diameter.

- Leigh

*available in sizes as small as 0.15 microns, if you have a thick wallet ($95 ea). These filter out bacteria.

[Robert Bowring]

Yes. I was referring to the faucet cartridge.

[William Whitaker]

This is just a thought... Years ago for my darkroom at the time I built a water panel. It had a central mixing valve (not thermostatic) and a tap. There were also other mixing devices in parallel downstream. I found that setting the mix temperature with both hot and cold valves partially open allowed hot water (which was at higher pressure) to feed back into the cold line with the result that my downstream devices were not receiving hot and cold supply, but hot and warm supply. Temperature differential was lost and control went out the window with that one.

The solution was to install one-way check valves so that reverse flow could not happen. After that the system worked fine.

The point of this is to ask if perhaps there might be check valves somewhere in your system and if so, have they gotten stuck open, perhaps because of sediment which found its way into the system over the years? It's a bit of a reach, but here we are at two full pages to this thread and you're still trying to crack it...

It seems in thinking back over this ancient scenario that someone once told me that hot water is always at a higher pressure than cold. Is there any truth to that statement? It could stand to reason since hot water is hot. And hot things expand. But I could've dreamed it.