point-of-use/on-demand water heater for fish room?

[jjohnwm]

I want to upgrade the method used to provide water to my fish room. I currently have several 50-gallon drums which I keep filled with water, heated and ready to use as required, but I am limited as to the total gallons available to me at one time. Energy consumption is very wasteful if I keep the drums heated constantly, but if I leave them cold then it takes a day to warm them up so I don't have instant access in case of an emergency. They also take up a lot of space. I am on a well, and don't treat my incoming water in any way other than heating it; additionally, the incoming feed line for the whole house runs through an electronic de-scaler.

I am considering installing a small point-of-use tankless water heater that would then give me unlimited water at any time. Small units that are designed for a single wash-up sink seem ideal; they are very compact, operate only when heated water is actually being drawn, and are available in 120v versions so can use my existing wiring (I have a 10-gauge circuit already fed into the fish room). Ideally, I would like to find a unit with an integral adjustable thermostat that would allow me to set the temperature, but most of the units I can find have a minimum temp setting of 86F...way too warm for my purposes. The solution seems to be a separate, thermostatically-controlled pressure-balancing valve to mix hot and cold to create my desired temperature. This is more of a PITA, since I will need separate pipe runs for hot and cold running to the valve. To operate correctly these valves require specific water pressures and flow rates, and the heater must be sized properly to match. All of this is complicated by my domestic pressure-tank, which cycles up and down from 30 to 50 PSI...and of course, my well water temperature varies from season to season.

In my mind I am picturing a system that allows me to open a valve and have instant access to endless water at the perfect temperature. I can't be the first person to go down this particular rabbit-hole. Does anyone have any suggestions or comments? Either refinements to the system I am envisioning, or else ideas for a completely different method of achieving this goal?

 

[fishdance]

I would go the other way, using a slow constant/continous drip water change 24/7 that displaces old tank water to waste (could be collected and re-used).

So no need to heat your incoming water. The fish tanks heating will cope. No water storage space required either. Also the waste water line can be quite small if your drip rate is slow.

I don't know if your water pipes freeze in winter though. I'm in Australia but previously in cold climates with occasional snow, I used 100m coil of 4mm micro polypipe that brought the water to room temp before entering the tanks. The flow is steady but very slow. The condensation collected was good for soft water species.

 

[jjohnwm]

I would dearly love to have a constant drip changing my water for me. I had that in my previous house and it was lovely, but sadly it just isn't practical for me now. Waste water all needs to be pumped up out of my basement, and I can't allow 400+ gallons of excess water to overload my septic system each week; it needs to be pumped out into my adjacent field, through pipes which will be frozen solid for 5 months of the year.

Also, my incoming well water at the moment is at 37F, so snaking a line around in my basement and expecting it to warm up to useful levels just won't allow enough flow to be of any value. Most of my tanks are not equipped with heaters. I just maintain a basement temp of 70-75F in the summer and around 65F in the winter, and keep fish that are suited to that range. This method works well, but it is much slower to react to and correct for cold incoming water than individually-heated tanks would be.

 

[BIG-G]

I tried it with one that was given to me,


The problem I had was that the dwell time had to be reduced so much to get the water to temp that it was just a trickle.
Since this was a freebie and it wasn’t big enough or powerful enough I give up on it.

I believe sized properly and thermostat adjustable, it should work.

The way I get around having pre-heated water is to do changes more often with lesser amounts.
Overall the tank temperature only fluctuate a degree or two.

 

[pacu mom]

We went with a tankless water heater for our fish room addition. Endless source of hot water was appealing to me. Ours is not point of use, though, as we needed hot water for the new utility room and the master bedroom/bath. We put in hot/cold water lines directly above the main tank, and will have lines to the sump and the utility sink (still a work in progress). There is not way a regular water heater can supply the hot water we need for the big tank, as we run out of hot water changing water on the small 300 gallon tank.

Hot/cold water 2' above the top of the tank

 

[fishdance]

The drain height can be set to any level including well above your fish tank's water level with a header tank kept full by small water pump.
Just think about how they plumb multi tank filtration.

If you are not heating your tanks then the fish could handle cool water anyway?

Hopefully you can find something that works well for you.

 

[jjohnwm]

My fish can handle coolish temps compared to most "tropicals", mid-60's or a bit lower for part of the year. But I want the freedom to do 50-75% water changes on my tanks, and doing that with 37F water just isn't an option.

Drainage height isn't an issue; the problem is that the permanent drainage lines that carry away my waste water (as well as groundwater that collects in my floor sump pit during spring) are frozen solid for 5 months +/- so I am forced to unroll 150feet of garden hose in the snow for every water change during that period. This, of course, is why I don't want to do multiple wimpy little water changes. The bulk of the job is laying and then picking up the hose; a 10-gallon water change is pretty much the same level of physical work and inconvenience as a 300-gallon one. This isn't going to change, it's simply the main reason why I want large quantities of water avaukabke.
.
And today I got a response from the manufacturer of the on-demand heater I was considering. They were brutally honest; the product is poorly suited for my situation from almost every conceivable angle. I will definitely need a mixing valve and likely a 220v circuit.

Ah well, got some cipherin' to do...