Propane on demand water heater eval

[JL43062]

I'm looking into replacing a 30g electric water heater with an on demand propane heater. I'm a diy'er. The place I'm looking to do this at is relatively remote/small--but not "that" remote if it has utility electric. I'm working toward the place having self sustaining utility options (i.e solar, wood burner, well, cistern) to leverage with grid connected utilities . Some of this is in place or in process... I mentioned the place being small and I'm looking to free up space taken by the 30g water heater. Basically weighing the pros/cons... I mentioned the reduction in space being favorable. It also seems the installation won't be difficult as it's located in the corner of the structure on/near outside wall--water, fuel, electric, venting are very close. My main concern is that the place relies on rainwater captured in a cistern... And I haven't installed filtration for the house plumbing. To this point I only treat the cistern water with bleach (note: wish I knew how to do this optimally). There are several things I question... To start--how reliable are propane on demand water heaters? What breaks on them? Is there maintenance/service that can be performed by a homeowner, or are they considered "disposable"? What is their tolerance to midwestern rain water? The rainwater is collected off of steel roofs... then filters through stainless gutter guards (there purpose is to filter leaves from gutters), then cistern acts as a filter for most organic stuff that makes it through with the stuff settling to the bottom. A pump then moves the water into a above ground bladder. The water from a faucet in the place has a green tinge to it, but is fine for brushing teeth, taking showers, washing dishes, etc. I filter it if I want to have drinking water. Perhaps I need to test the water to translate into something I can quantify in microns? (just thought of this now). So... I'm looking for advice on whether a propane on demand water heater is good for my use case. If so, what would I need to do (if anything) to the ingress water. If not, I'll continue using the 30g and will put a tub under it and buy some spare elements!

Any thoughts, additional considerations needing made, overall advice is appreciated. Thanks!

--Jared

[PLUMBER RICK]

Why not install the tankless outside. This way you don’t need to vent it and if it leaks, nothing harmed. Plus a gas fired heater is not allowed in a room designed for sleeping.
As far as maintenance, you need to flush them with a descaling solution such as white vinegar yearly depending on the mineral content / water hardness.

Personally, a tank heater is next to maintenance free compared to a thankless , yes Thankless heater. Plus a tank heater can run off a decent solar array and can operate with minimum flow, store water. A thankless would require flow and doesn’t like cycling on and off. Plus has to be clean power for all the electronics inside.

Rick.

[blue_can]

Since you are into self-sustaining and mentioned solar - how about a heat pump water heater. At higher outdoor temps you will use much less energy with an HP water heater than straight electric.

Tankless can be maintenance free and last a long time - some of that depends on the water. I installed a NG tankless in the summer of 2003 and it has been trouble free and still runs without issues. I know of others who have had to change out tanks more than once in the same time period. The water you describe may cause the heat exchanger to corrode relatively soon. The only maintenance I know of that would be a good idea would be heat exchanger flushing with something like vinegar to flush scale from hard water. So when you install it, add some access ports for this procedure.

I use a small pump and bucket setup to do this but since I also have a water softener, I don't gain much by this procedure and have only done this about 3 times. Another thing to do would be to clean the inlet filter to the tankless on a regular basis.

[JL43062]

Thanks for the responses. I see both of your location is sunny SoCal! You're likely bringing installation in that climate perspective... And I definitely should have stated that the region I'm in can get below 0F in winter--I estimate it does this every ~5 years and multi-day sustained subfreezing temps are common each winter season.

In response to Rick: Mounting the unit outside would simplify installation, but assuming the device has protective measures to avoid freezing, it would add complication to ensure exposed plumbing wouldn't freeze. I like the leak protection... It would be mounted in a mechanical room/storage closet--two doors between it and bedroom. Mention of tankless not doing well in "cycled" environment is a great point... at the location we practice water rationing with a shower head valve--frequently cycling flow. I can see how this could reduce life of tankless.

In response to Blue:
I'll look into a heat pump option. My knowledge of heat pumps is very low... But I looked up the basics before responding here and I think it has a lot of potential. It may be ideal. Reason being, it seems it can could replace a dehumidifier I've been running at the place... At this very time of the year, the concrete slab foundation is still very cold. When this cold slab comes in contact with the ambient humid air, a bad thing happens (condensation). I also run a window air conditioner that seems could be reduced with a heat pump. Would likely need to add fans for better inside ventilation... Good food for thought! So this might be perfect and I'll look into it further. Between you and Rick's responses, I'm not favoring the tankless anymore... As I mentioned above though, I don't expect the impurities of the water to be "mineral" that causes hardness of the water. I could be wrong, but hard water is associated with water pumped from the direct ground, or water that has had a lot of contact with earth up until use. The water at the location comes from evaporation, then falls as rain. I believe this removes mineral? It is then collected from a metal roof and stored in sub-grade ground tank with concrete poured walls (cistern). With this, I believe the impurities to be mostly "organic" --thinking algae. Even though cistern is very dark, there is probably enough light seeping in for life to form. Folks in the area generally treat cistern water with bleach. I do this too, but without measure or consistency.

Thanks again for the responses... Sorry slow to get back--had family event to tend to. Although I'm trying to position the place to be off-grid, this type of discussion always shines light on how much energy dependency there is... even in a tiny place.

Take care!

[blue_can]

Thanks for the responses. I see both of your location is sunny SoCal! You're likely bringing installation in that climate perspective... And I definitely should have stated that the region I'm in can get below 0F in winter--I estimate it does this every ~5 years and multi-day sustained subfreezing temps are common each winter season.

In response to Rick: Mounting the unit outside would simplify installation, but assuming the device has protective measures to avoid freezing, it would add complication to ensure exposed plumbing wouldn't freeze. I like the leak protection... It would be mounted in a mechanical room/storage closet--two doors between it and bedroom. Mention of tankless not doing well in "cycled" environment is a great point... at the location we practice water rationing with a shower head valve--frequently cycling flow. I can see how this could reduce life of tankless.

In response to Blue:
I'll look into a heat pump option. My knowledge of heat pumps is very low... But I looked up the basics before responding here and I think it has a lot of potential. It may be ideal. Reason being, it seems it can could replace a dehumidifier I've been running at the place... At this very time of the year, the concrete slab foundation is still very cold. When this cold slab comes in contact with the ambient humid air, a bad thing happens (condensation). I also run a window air conditioner that seems could be reduced with a heat pump. Would likely need to add fans for better inside ventilation... Good food for thought! So this might be perfect and I'll look into it further. Between you and Rick's responses, I'm not favoring the tankless anymore... As I mentioned above though, I don't expect the impurities of the water to be "mineral" that causes hardness of the water. I could be wrong, but hard water is associated with water pumped from the direct ground, or water that has had a lot of contact with earth up until use. The water at the location comes from evaporation, then falls as rain. I believe this removes mineral? It is then collected from a metal roof and stored in sub-grade ground tank with concrete poured walls (cistern). With this, I believe the impurities to be mostly "organic" --thinking algae. Even though cistern is very dark, there is probably enough light seeping in for life to form. Folks in the area generally treat cistern water with bleach. I do this too, but without measure or consistency.

Thanks again for the responses... Sorry slow to get back--had family event to tend to. Although I'm trying to position the place to be off-grid, this type of discussion always shines light on how much energy dependency there is... even in a tiny place.

Take care!

To clarify in this context I was referring to a heat pump water heater since you asked about water heaters. But heat pump HVAC could also make sense for your situation.

[suas22rt]

interesting information