Pumps for darkroom chemistry…

[Ai Print]

I did a search and did not really come up with any real answers so here goes.

I had my plumber run some 2.25" PVC from the darkroom in the basement to the garage in order to easily place a couple of 1/2" or 5/8th" flexible clear tubes for disposal of spent chemistry. The developer and stop with go in one tank and the fix in the other, probably 5 gallon holding tanks above and below.

All I can really find to pump are 12V DC RV water pumps that flow at about 3 GPM which is about right for a rate. So what I am trying to find are 110V AC pumps that might fit the bill and are easy to find and replace. I am trying to avoid some obscure pump that might be hard to replace if it goes bad.

The pumps will be underneath the tanks so they do not have to be immersible and given the nature of chemistry, would be best if not.

Any tips on pumps like this?

 

[Mike Bates]

Chugger pumps are popular with the home beer brewing community. The have stainless steel or polysulfone heads, depending on the model. They aren't self-priming, but placing them below the tanks would work fine. The heads can be disassembled for cleaning, which is especially important to brewers. They are relatively inexpensive.

There are other brands used by the beer brewers, but Chuggers are quite common. I'd look in that direction.

 

[Mr Bill]

So what I am trying to find are 110V AC pumps that might fit the bill and are easy to find and replace.

Hi, I'm not going to recommend specific pumps; the sort of thing we used in professional photofinishing are probably way more expensive than what you want to spend. (We used a lot of March pumps - 4C models were commonly used for circulation in many big Pako processors; 3C and 5C were useful submersible pumps; they're expensive, but can run all day for years.) But I'll point out a few things you might want to know.

First, if your pump is outside of the collection tank, this means multiple connections that have to be leak-free, as well as valves to isolate the pump from the system in order to replace a bad pump. So a lot more plumbing than a simple submersible pump.

Regarding flow rates, a single number typically means with no "head pressure," in other words at the same height. Since you want to pump from your basement to garage, I'm guessing a height (aka "head") of around 10 feet. So make sure your pump can do this; there should be specs available for it (ideally including flow rates at different head pressures).

Most pumps, especially "centrifugal" pumps, are subject to what are known as "air locks." A centrifugal pump basically has a spinning impeller that tries to fling the liquid out to the side - this is what creates the "pressure", while fresh liquid enters at the center. But... if an air bubble gets trapped within the impeller cavity, the pump won't be able to pump against any resistance. So you ought to install the pump in a such a way that any air bubble will automatically rise out of the impeller area. If you can't do so, you'll need a way to "bleed" the pump.

You also need a way to turn the pump on and off. In our systems we used various level-sensors, with a high and low level setting - the pump turns "on" as the high level is reached, and "off" at the low level. So the system never needs intervention until the pump fails. Note, the best protection against pump failure is probably an "overflow" fitting in the collection tank that goes to a backup collection tank, and has an alarm built in. Also, on the topic of leak protection, you want a way to prevent overfilling the collection tank in your garage. Ideally it would also have an upper-level sensor that could lock out the pump. As a secondary protection, the collection tank would also have an overflow pipe going into secondary collection.

A couple last notes: when you pump up, don't let the garage tank be able to get siphoned back to the basement tank (where it may overflow or keep turning the pump back on). The most reliable way to do this is to dump the liquid in ABOVE the solution level. If you don't want the splashing there you can run the hose down in, but put a small hole in the pipe/hose above solution level to break the siphon.

Last note: many pumps can be damaged by running dry, so make sure you know the situation with yours and take whatever steps you need to.

I'll be glad to make opinions on any specific questions.

Ps, you might want to look at submersible pumps at your local garden center - they're commonly used in garden ponds. (Check the specs on chemical resistance, they're likely ok with possible exception of high pH developers?)

 

[Kawaiithulhu]

I've seen peristaltic pumps used in several DIY automated system projects. They don't have the air lock problem centrifugal pumps can get, aren't damaged by running dry, and they prevent back-flow without extra valves.
Something to add to your reading list.

 

[Mr Bill]

I've seen peristaltic pumps used in several DIY automated system projects.

Hi, imo peristaltics are just too little for serious work beyond certain metering applications, and they need maintenance (periodic replacement of tubing). I just don't think this is a good application. (If the apps you saw tell a different story, can you give a link? OP thought about 3 gal/min was about "right".)

 

[keko]

http://www.iwakiamerica.com/

 

[JOR]

http://www.iwakiamerica.com/

You might try the oscillating pumps manufactured by Iwaki and Gorman-Rupp. The flow-rate is modest but they are self-priming and can operate dry - the noisy rattle when dry is a built-in alarm. They have rubber bellows and flap valves of polyisobutylene or styrene-butadiene and were designed to carry away the condensate from A/C systems but withstand photo-chemistry quite well, although they don't like stop bath without developer admixture.

 

[Ian Grant]

I used a lot of March May pumps when i built Gold refineries, they were also used in the photo processing machines. They weren't cheap but as I bought a lot I had OEM discounts which was 50% at the time. There's also Serfilco.

You want Magnetic coupled pumps as they will stand up to corrosive chemistry, photo chemistry won't affect them at all, I was pumping hot Nitric caid solutions and aqua regia (mix of Hydrochloric acid and Nitric acid< and never had any problens.

Ian

 

[Ai Print]

Thanks folks, I'll take my time on researching a bit more and then give it a first go.

 

[Mr Bill]

I'm guessing this is probably more than you want to spend, so it's not a recommendation, rather an example of something that could be used.

Way back, I designed the chemical mix room in what we called a "small" processing lab - about 50 employees. Rather than put elaborate controls on the pump-out system, we gave the mix operator a simple on/off switch and took a chance on a pump brand we had never used. They were Little Giant magnetic drive pumps said to have a "run dry" capability (up to 8 hours). So when the operator would invariably forget to shut it off, the pump wouldn't be destroyed. They worked great, and as far as I know never had to be replaced during the lifespan of the lab.

It's model #3-MD-MT-HC. (Only the HC version is "run-dry." ) The link below has them for about $150 (US), roughly the same price as we paid 1980ish, as I recall.

https://www.amazon.com/gp/aw/d/B000...3-MD-MT-HC&dpPl=1&dpID=41tbNiip6ML&ref=plSrch

Specs are here, there is a flow vs head graph showing a flow of roughly 5 gal/minute when pumping to a height of 10 or 12 feet: http://littlegiant.com/media/130834/995778.pdf

Manual is at. http://littlegiant.com/media/130831/993236.pdf

It's good practice to put a valve between the tank and pump so the pump can be serviced, if needed. Also a tee with another valve and pipe nipple so you can attach tubing and drain the tank if desired.

 

[Mr Bill]

With the other pump types having been suggested, I think a few words may be in order on the magnetic-drive centrifugal pumps. There are no seals to wear out and leak. There are no valves or diaphragms to fail. The only moving part in the pump chamber is the impeller, driven by a spinning magnet outside of the pump housing. And the pumps are pretty quiet.

The downsides are as I mentioned before. If you are pumping against some "head," you have to select a pump based on this (other pump types, positive displacement, don't care very much about head pressure). And many of them can be damaged by a short period of running dry - the Little Giant model I mentioned is an exception to this. And you have to install in an orientation that prevents an initial "air lock," so either understand how this works or do it according to the manual.

This style pump has long been the workhorse of the photofinishing industry for good reason.

 

[mgb74]

Given the variety of 12v DC pumps for marine applications, would it be worthwhile to use one with a step down transformer or even a computer power supply.

 

[mshchem]

Hi. I've been buying mag drive pumps out of scrapped Noritsu processors off Ebay. Magnetic drive pumps wont leak, no shaft seal. The ones I have got (two) are 24 V DC 11 L /min. I bought a old 19V computer power supply to run mine. Most of the Fuji pumps are 100V AC (Japanese standard I believe) The reference above to Iwaki is spot on as I believe both my pumps were made by Iwaki. The little pumps are designed to run developer and blix all day long so chemicals aren't going to hurt them. I paid 15 bucks a piece for my little pumps. I'm just fiddling around. If you have money to hire a plumber I'm sure you could find a nice mag drive pump that would work.

 

[Mr Bill]

I've been buying mag drive pumps out of scrapped Noritsu processors off Ebay. Magnetic drive pumps wont leak, no shaft seal. ... The little pumps are designed to run developer and blix all day long so chemicals aren't going to hurt them.

Definitely they're great little pumps and have all sorts of applications. But ... I'm real skeptical that they will pump to an 8 or 10 foot height. You could try one of yours out pretty easily if you've got enough space and tubing; just raise the output line above 10 feet ot so. It might save the OP some time and effort.