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 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.