Tankless Hot Water Heaters?
I have a darkroom sink that currently is cold water only. There are hot water pipes in the basement, but not nearby. I am trying to figure out the most cost-effective way to have a temperature-regulated water supply in my sink. 1) I could pay a plumber to bring hot water across the basement with copper pipes. 2) I could run an insulated hose from a spigot on the hot water pipes and install a mixing valve (the Arkay photo wall-mounted systems seem expensive, but plausible). Or (3) I could install a tankless hot water heater (ground temp of the water in winter is about 50 degrees F) and attach it to a mixing valve. Any advice?
Why not just keep it simple? If you can make a hose work, why spend $1,500.00 + installation costs?
The tankless hot water heater will require either a 120v circuit (for ignition) and an LPG line, or upwards of 100 amps @ 220v to do its thing.
First you should decide on the type of mixing valve. In the past, I have used a common kitchen faucet, an Arkay type unit, and finally a Hass Intellifaucet D250 mixing valve. I'm very satisfied with my Hass valve, but a common kitchen faucet or bathroom shower mixing valve is certainly usable if you can monitor the temps occasionally.
Once you decide on the mixing arrangement, I would bring the hot water to the darkroom by installing a copper line from your present hot supply. This would be cheaper than the tankless system, and would probably give a more consistent and stable temperature to your mixer. Stay away from the insulated hose, unless this is to be a very temporary setup.
Agree. I use the kitchen faucet (actually a utility faucet because it has a hose thread on the spout.) Once things settle down it will hold temperature very well. The price is right too, I got mine along with a like new stainless steel sink at Habitat for Humanity for $35.
Originally Posted by resummerfield
It's not hard to run a copper pipe, and as resummerfield says, you'll probably get more consistent temperatures. The hose idea sounds pretty temporary, and the copper pipe will cost less than the tankless system once you pay for the electrical and gas if you need it. Just IMHO.
Where to begin...
My initial thought is that based on my experience with a whole-house gas fired tankless is that you might be better off with a small tank unit.
But since your requirements are rather different, it may work out. Plus, I'm assuming you are speaking of one of the small electric units.
First off, what we've found with our unit is that it does not maintain the set temperature well. I don't know if that's due to a fault, or the system's design or what. But when set at 122 F it varies from that up to scalding. What it means for the darkroom is that you can't rely on what the faucet will get. I have a temp control mixing valve which could possibly handle it, but that leads to factor 2;
2. Tankless heaters need a minimum flow to operate, my ground water is about the same temp as yours, but even so, getting to 68 degrees or so, doesn't require much hot water. For things like print washing and film washing, the demand isn't enough to cause the heater to come on. Our unit needs about .5 gpm to activate, as I recall.
This will probably be the major consideration for you. For print washing, I compensate by turning on the hot water for a bit so the pipes are charged with hot water, then letting the print washer run off what's built up, but after 10 or 15 minutes, the water is ice cold. It helps to do print washing while doing laundry. Since you're only using it for the darkroom, however, additional use probably isn't an option.
I just looked at the small units Home Depot sells, but they don't list the minimum flow requirement.
3. The third problem area is that our unit seems to delay restarting by a few seconds if you stop the water and restart it. This means you get a slug of cold water in the middle of the heated stream. For the darkroom, that may not be so bad, but it's a PITA if you're showering or washing dishes. Tankless units may save energy, but they do not save water. I don't know how the small units will react to intermitant use. For the darkroom situation, I don't think it would be a major problem, since the use isn't very intermitant. But it would be something to watch out for, especially for film washing, if you aren't using a good temp controller.
4. Tankless units are sensitive to scale. If you don't feed it softened water you'll need to de-scale it with vinegar periodically. Also, it will dump pieces of scale into the water (since there is no tank for it to accumulate in). You WILL need a hot water filter between the heater and your faucet.
If you go with the tankless unit, you will need a pair of these valves to accomodate the de-scaling; http://www.plumbingsupply.com/isolationvalves.html
My humble advice is to not let the plumber talk you out of them.
That said, I've been considering a small electric tankless unit to serve just my darkroom. My space is very limited and it would be a lot easier to accomodate.
Your mileage will vary, but this is a good description of my experience so far with the tankless world.
If you ever consider a whole house unit, Fine Homebuilding magazine did an excellent article a couple of years ago on integrating a whole-house tankless heater. One of their recommendations is to combine the tankless unit with a small tank unit to accomodate the low-flow and intermitant use situations. The article should be available on their web site, though it mostly won't apply to your specific plans.
Finally, wer'e spoiled here in the U.S. Tankless water heaters have been common in the rest of the world for some time.
P.S. If the unit you are considering varies the water flow to regulate temperature (our whole house unit does), a pressure sensing mixing valve like what is common for showers will not work well. It will end up fighting with the water heater, and the manufacturer of ours (Bosch) recommends against them. A temperature sensing unit, like the Arkays and similar is ok, but more expensive.
Yes, retro-fiting a gas fired unit is extremely expensive. For ours, the installation cost as much as the unit, and we under-spent. Heating water from 50 degrees to 120+ while it's flowing through the space of a large camera case needs serious heat, and serious gas flow to do it. The BTU rating on ours is close to double that of the furnace that heats the house.
Some of the small electric units run on 110 though. Since the darkroom water heating demand is modest, that may not be an issue.
Last edited by bdial; 09-22-2009 at 06:39 PM. Click to view previous post history.
Reason: additional comments and corrections
Sponsored Ad. (Subscribers to APUG have the option to remove this ad.)
Find a licensed plumber who moonlights or does side jobs. Hose would only be for temporary use and you would need to use the proper hose for hot water (more costly), not just garden hose.
If you cannot run the water line yourself, you won't be able to properly install a tankless heater either.
The home where I grew up used a tankless heater. They are quite ofeten used in industrial settings or hotels / motels for instat hot water in infinite supply.
We never had any problems with it in spite of it being over 40 years old. The only problem was that temperature varied with flow rate and if you were not careful, and turned the flow way down, you could get steam. This unit was so old it did not have a safety temperature limiter on it. I used it to develop my first E1 Ektachromes and Type C prints in the 50s.
I agree with bdail, when I worked in a lab the tankless (gas) setup was good for our E-6 processor But a pain for bxw (lower flow and temp). When I built my home darkroom I put in a 19 gal. hot water heater. It has been fine for me although I should have opted for something a little bigger.
Wow. For a reply to a first post here, you all certainly have provided a lot of food for thought. My situation is pretty idiosyncratic. First of all, I am in a rural setting in a house on a well with a 20 year old solar hot water system. We do have a water softener. Although there is a back-up electrical coil in the hot water tank, the temperature of our water varies seasonally (cold water by about 7-10 deg. F)/hourly depending on how much sun is hitting the house. I have gotten by for film developing by using a Jobo CPA-2, which does OK at maintaining 68 F, but I recently flooded the electronics unit (user error - don't even ask [sound of gnashing teeth]). Needless to say replacement Jobo CPA2 parts are scarcer than hen's teeth. Oddly, I do have a massive (and currently unused) film processor (Jobo ATL 2200 -- don't know what possessed me) that requires tempered water to use. Perhaps an electronic mixer that would take into account our variations in water temp would be the way to go. All I can say, is that I have learned more about the ins and outs of plumbing, electricity and water chemistry than a city-boy ever wanted to know since moving to rural Vermont. And snow tires. I now understand snow tires.
Is this tank a Hot Water Tank or something else?
Originally Posted by Ben Marks
Last edited by fotch; 09-23-2009 at 10:33 AM. Click to view previous post history.