At this time I have a Bock oil fired water tank in our home, for about eight to nine years. We also have a deep well and our own septic, what I'm getting to is water pressure, deep well pump on at about 45psi and off at around 64psi. With the low pressure at 45, would that be too low for a tankless waterheater? I've read on here that the heater will shut off if pressure is too low. Also, a second question on the cold water return for faraway sinks, is there a thermostat you can install inline so the water is there waiting, or a push button, like I saw in Mechicanics Ill.
Lowe's, has a unit that is advertised to be able to supply two different hot water demands at the same time, just not sure which way to go, oil or propane.?
Greg

Your water pressure is well in the range needed for the tankless water heater, most city pressures are in the 50 lb range. You are right about the heat shutting off if the water moves through the water heater too slow, but that has more to do with volume than it does pressure.
There are two ways to have "Instant Hot Water" one is to have another water line returning the water back to the heater by way of a small pump, and this would have a thermostat attached to it so you can set how hot you want you water to circulate through the pipes.
The second way is to connect the hot and cold water lines together under a vanity in the fartherest bathroom from the water heater. You put a small pump on the line that connects the hot and cold and the pumps then takes the water out of the hot line and puts it into the cold line and that goes back to the water heater. The one drawback to this is the water is hot in the cold water side for a few seconds to a couple of minutes until all of the water in that line is replaced with cold water. Most instances that would be OK because you are going to be washing your hands or something anyway.
If you want more info let me know.

Thank you letmetellu,
Great info, I mite need your help later setting the tankless heater up..
Greg

Letmetellu is doing such a great job of answering your questions that I hesitate to intrude but I thought I'd add a little something about recirculating systems.
Many people wait for hot water just as you do each morning. A similar thing happens when people operate other sinks, dishwashers and washing machines. Fortunately this problem can be solved one of two ways depending upon how your plumbing system is designed. Keep in mind that the work to achieve your goal is not something the average do-it-yourselfer can tackle. What's more, certain cities and states have strict regulations with respect to modifications made to water supply systems that are connected to public water systems. Be sure to call your local plumbing inspector before you cut into your piping system.


This cool pump connects to your water line just above your water heater. You will need an electrical outlet to be installed nearby. Do not use an extension cord to power the pump.
Clean water is a valuable natural resource and it should not be wasted. The trouble is, in many localities, water is a very cheap commodity. When prices are low, people tend to waste. For example, a cubic foot of water costs me just a little over 1.6 cents. There is a very good possibility that you waste less than a tenth of a cubic foot of water each morning. To prove this, assume that there is 25 linear feet of three quarter inch piping between your shower faucet and water heater. Do the math and you will find out that there is just .076 cubic feet of water inside the water pipe. To waste one dollar's worth of water, one would have to take over 800 showers.

To get instant hot water as you often find at hotels and other institutions, you need to have a loop in the piping system that circulates hot water back to the water heater. Most houses do not have a loop as the hot water pipe typically dead ends at the plumbing fixture that is farthest away from the heater. It is possible to install an effective return loop in single story houses that have a basement or crawl space where the water supply pipes are visible below the floor joists. Two story houses make this task nearly impossible, as the piping system is typically hidden in the walls of the home.


But you don't have to install a return loop if you choose to use a modern recirculating pump system. These products employ a nifty temperature actuated by-pass valve that connects the cold and hot water supply lines at the fixture that is farthest away from the water heater. The bypass valve uses the cold water line as the return loop back to the water heater.

Not all recirculating pump systems are the same. One system places the pump under the sink at the farthest fixture. You have to push a button to start the pump. The trouble with this system is that you still have to wait for hot water. What's more, this pump needs high voltage electric to operate. It can be a huge challenge to install an outlet under a sink.

Another system activates a remote pump that can be near the water heater. The trouble with this system is that it pumps water through the system whenever the temperature drops at the activation valve. This system wastes energy dollars as it pumps hot water while you sleep and are away.

Perhaps the best pump system is one that has a temperature controlled by-pass valve under the farthest fixture sink and a timer on a pump that can be conveniently located adjacent to the water heater. The timer can be set to go on and off at 15 minute intervals depending upon when you feel you need hot water at the fixtures. The pump is equipped with a handy extension cord that can be plugged into a convenience outlet near the pump. There is no water waste with this pump and it also minimizes energy waste since it only sends hot water into the water supply lines during the programmed times.

Gravity hot water recirculating loops that do not require a pump can sometimes be installed after a house is built. They will only work when the water heater is below the water supply lines. This system requires that the hot water line return back to the heater after it services the farthest fixture. The return line connects to the bottom of the water heater at the drain valve. Natural convection drives the system. Energy loss is a minimum if you insulate the entire hot water loop except for the last 15 feet of pipe as it re-enters the water heater.

Hope this helps, Tom