Maintaining 68° with tankless water heater

[Mark_Turner]

I have a tankless gas water heater in my studio building. Yesterday I processed my first film in this space (and first in many years). I had a lot of trouble maintaining 68°F water flow to dilute solutions and for wash water. The problem is that the tankless heater requires a certain volume of water flow to turn on, a flow that's quite a bit higher than needed to buffer the 55° water coming from the cold tap. I'd crank up the hot to get it flowing, then turn it down to get 68°. Soon, the water heater had shut off and the temperature dropped again.

I managed to get enough water at the right temperature to get my developer the right temperature and didn't worry too much about the temp for the other solutions since they were in the 70° range. But I need a solution to the problem.

If you have a tankless water heater serving your darkroom, how have you dealt with the water flow and temperature problem?

[Tin Can]

I don't have tankless, but do use a Hass Mixer (http://www.hassmfg.com/) that can flow low amounts

Right now I am waiting on a couple fittings to pipe the Hass output into a tempering bath tank that allows constant flow and temp control with 4 film tanks sitting in the open top tempering tank

The Hass water flows in the bottom and out much higher

I am using 1/4" od RO tubing with a manual output control valve

I doubt my consumption rate will rise much and locally the more water I use the lower the cost per 1000 gallons

[Luis-F-S]

Have a traditional tank water heater for the issues you mentioned. Even with a control valve, I suspect the TWH will shut off due to the low flow rates. Check with the TWH manufacturer to see if they have any low flow mods.

[Doremus Scudder]

I lived in Vienna for 30 years. Tankless water heaters were standard there.

There's no way you are going to get reliable temperature control at a low flow rate and a relatively low temperature. Forget it.

My solution was to fill large plastic tubs with water and bring them to the proper processing temperature. I then mixed my chemicals, etc. with that. For washing film I did the same, filling the tub and making sure it was the right temperature before pouring it slowly in the washer. I used a 30-minute fill-and-dump regime for film washing and had to manually dump and refill the washer every five minutes.

For prints, you could easily do something similar; prints are even less finicky where temperature is concerned.

Really, it's not that much trouble and works just fine.

Doremus

[Mark_Turner]

Doremus, that's certainly one possible solution — if you have the space for the large tubs of water, which I don't. At the moment I'm processing at an old kitchen sink in my office (35mm in stainless tanks) as I prepare to turn a small bathroom into a darkroom suitable for processing sheet film.

[Tin Can]

What temp is your home kept at?

Put 5 gallon tanks on top of shelving, water will stabilize at room temp

Gravity works too

[urnem57]

The gizmo from Cinestill works quite well. Others report that a sous vide (sp?) heater used for cooking works well for maintaining temperature control.

[Tin Can]

I wanted to buy a tankless water heater more than once and have used them in EU

I may install a propane tankless water heater on my camper, which MAY become a DR

By ON, I mean on outside as it is meant for outside showers and is not safe inside, but it could do 2 things, I always like things than can do 2 too

[Eric Woodbury]

I have two tankless, propane fired water heaters. Impossible for darkroom. A 5 gal electric water heater in my darkroom I turn-on as needed.

[Mark_Turner]

What temp is your home kept at?

Put 5 gallon tanks on top of shelving, water will stabilize at room temp

Not a viable option in the rather cramped room that will become the darkroom, nor in the space I'm using temporarily. But for other folks it could work.

The air temp in my studio workroom, the room with the kitchen sink, was 70°F yesterday but it varies seasonally with the outside temperature.

[Mark_Turner]

I have two tankless, propane fired water heaters. Impossible for darkroom. A 5 gal electric water heater in my darkroom I turn-on as needed.

That's the option I'm considering, with the on-demand water heater feeding into the electric as a pre-heater when there's sufficient flow.

[Jim Noel]

Careful processing does not require a 5 gallon tank.
I fill a 2 liter container with water at correct temp. I mix chemistry for processing and collect 2 more liters for use in washing. To wash I use 5 changes of water. On occasion I need to draw some more water at correct temp, but certainly not 5 gallons. I use a fill and dump process to wash.

[Leszek Vogt]

Mark, this may be a home made remedy, but it may help. Essentially you keep everything in trays the same temp.

https://www.amazon.com/s?k=seedlings+temperature+control&i=specialty-aps&srs=21560361011&ref=nb_sb_noss

[mpirie]

I use a tankless water heater which is fine for running water at 20 ˚C in summer, but because the incoming water is around 5 ˚C in winter, the heater struggles to heat the water enough when it comes to washing film.

The heated water passes through a ProCo thermostatic mixer, but as the temp drops, the flow is restricted (unlike the Hass).

Chemicals are heated up in the recycling of water in a Jobo, so water for the dev, stop and fixer are all on temp.

Mike

[Tin Can]

Many ways to control fluid temp

For decades I designed, installed and operated rapid high volume valved systems that moved fluid from -35 F to 260 F in 30 seconds

Thermo shock IC engines, cost $1MM

Less is easy

Hass

[Luis-F-S]

That's the option I'm considering, with the on-demand water heater feeding into the electric as a pre-heater when there's sufficient flow.

That would be your best option, not the cheapest though. If your inlet cold is always under 68 Deg F, I'd invest in an Intellifaucet. I've bought the two I have used from less than 1/2 to 1/3 of the new cost.

[Mark_Turner]

That would be your best option, not the cheapest though. If your inlet cold is always under 68 Deg F, I'd invest in an Intellifaucet. I've bought the two I have used from less than 1/2 to 1/3 of the new cost.

Our cold water is always below 68°F as it comes from our well and we don't have all that many days each year when the air temperature is much above that. The issue is that the on-demand water heater shuts off when the flow is below a certain point (that I haven't determined). How does an Intellifaucet deal with that?

[Luis-F-S]

A Hass intellifaucet is a very accurate electronic mixing valve that maintains whatever temperature you set as long as it's between the incoming cold and hot tap temperature. It does nothing to make your tankless water heater work which is why you will probably need to add a small tank water heater. You can have the tankless WH in line with the tank WH, so you will have a supply of hot water once the Tankless WH shuts down. You should be able to add the small tank WH to your hot supply line. The intellifaucet will work at very low flows down to a trickle. You only need the smallest one for darkroom work, either the electronic K250 or the manual (budget) D-250. If your cold tap is always below 68 deg F, then you can maintain 68 deg by mixing the cold and hot tap from your tank water heater. Have you checked with the tankless WH manufacturer to see if they have any suggestions? The photo below shows a 10 gal water heater(the white tank) which feeds the hot tap for the darkroom. The blue tank is a pressure tank for the well pump. There is a single filter ahead of where the cold line splits to go to the water heater. I've since run a potable water line to this setup making the water filter redundant. Good luck.

212156

My darkroom design is in this thread:

https://www.largeformatphotography.info/forum/showthread.php?107412-Darkroom-Design-for-a-9-8ft-x-10-1ft-room&highlight=K250

[Jim Andrada]

Opposite problem here - the "cold" water can get up to almost 90 in the Summer. One "solution" has to been to use Ilford XP-2 in the summer since it's a c41 process. But that only works for MF:(

I've been thinking about installing a chiller. But for now I just run a couple of bottles of hot water and cool them down with ice cubes. It doesn't take long at all.

[Tin Can]

I am sure Jim, you have AC. I lived in Valley of the Sun when Swamp Coolers almost still worked

Storing water inside any HVAC environment will act as stabilizing thermal mass and be useable for B&W film and paper directly

Emulsions and processing are adaptable to any environment humans can survive naked

[Drew Wiley]

Incoming water too hot? Blend with a cold water drip line or accurate mixing valve. Ambient air too hot? Use a surrounding temepered water jacket with a blue ice brick in it, and if necessary either a cold or hot water drip line. Cheaper to do than running an energy-intensive water-chiller or thermoregulator.

[Jim Andrada]

Yes - this house has AC AND Swamp Coolers. We decommissioned the swamp coolers because they made the place so damp.

Inside temp averages about 74 - 75 but gets close to 80 in the summer, which can work, but times are pretty short. I have a couple of small plate heater/coolers (depending on polarity) so i was thinking of building a temperature controller. The Jobo has a heater, but alas, no cooler. Of course I could hang a bucket of ice water but I'd like a little more aesthetically pleasing solution (or rather, my wife wants one - I could care less what it looks like)

[Doremus Scudder]

Mark,

You don't need huge volumes of tempered water. Just enough to mix chemicals at first, and then enough for washing your film later. You can make a sinkful on demand whenever you need more; you don't need five gallons of storage. I had a two-gallon plastic basin that I used, but I could have got by with just mixing a couple liters at a time as needed.

FWIW, I don't think any kind of temperature regulator is going to work well with a tankless water heater; they're just too variable at low flow rates.

The best solution, if you have room, would be a dedicated small-tank water heater for use for your photo needs. Second-best is mixing tempered water.

Best,

Doremus