Using Gravity to Get Hot Water Faster 

Most of our customers find the heat loss is minimal and the benefit of a maintenance free system is worth it.

Exactly! Gas hot water heaters cost little to run but are inefficient. Electric hot water heaters are efficient but cost a lot to run. People water their lawns all summer long, do laundry, showers, and one flush of the toilet takes more than that. In the summer it works against your air conditioning. So let's be honest. The ONLY reason to have a hot water loop is because it's a pain in the neck waiting that long for hot water, and the temperature at which he terminated the first test was at less than body temperature, which means the person at the faucet would still be waiting well past 50 some seconds and your time is valuable too.

No really because the return temperature isn't that much lower so the heater doesn't have to heat the water up too often.

No, because the water coming back into the tank doesn't have to be re-heated much. It only comes back slightly less hot.

@@wadsworthplumbers But the pump is working 24/7 to keep the hot water fresh in the hot water lines, so even if nobody is using the kitchen faucet, the pump is working to keep fresh hot water in the hot water line 24/7 - surely your electric bill must have gone up since the pump has been installed?

@@mikefa5891 there's NO pump in this setup.

@@SergioSalvi ok i see - it is hard to believe that hot water will circulate without a pump.

Yes, that does improve re-circulation even more.

yes, I also think a shut off valve even an automatic one is needed so that the water heater is not heating recirculating water 24 hours every day.

A check valve is not needed since the energy to produce one way flow comes from the thermal gradient. The gravity system would be most efficient when the end user is above the tank. However energy costs are likely very significant, I will guess to a level of a few hundred dollars a year. Thin copper pipes radiate heat away very quickly compared to an insulated tank. The best way to do this would be to insulate all the outgoing lines from the tank to source, which would also increase the gradient and flow along the line.

We connected it just under the floor by connecting the recirc line to the 1/2" hot line.

@@wadsworthplumbers Thanks

It will help create a temp differential which will assist in the gravity operation. But, it's not absolutely neccessary.

Mackin & Sons Plumbing , thanx for reply and What u said does make sense, Let’s say on new construction, You run a third line to the farthest fixture.... both hot and third line are insulated well...hot and third line are connected Together at the furthest possible point ...the third line is connected to hot water tank low at the drain valve,,,,(put a T fitting where drain valve is located on tank) ... would the temp differential in the tank itself push hot water sufficiently to accomplish what we want here? Basically we brought the tank to the fixture essentially... but now there’s 2 hot water supply lines for the hot side of all fixtures and one cold ? What do u think on that.. I think putting a check valve on the third line would hinder the differential flow... When heater is heating ... the top and the bottom are vastly different in temp.. cappallary action or reverse osmosis (lol) What’s your thoughts I’d like to hear from you... thx bud

would only help after the lines were primed with hot water. you wouldn't want to insulate the new return line as it needs to lose heat to work driving the thermosiphon.

@@jfdesignsinc.innovationsid1583 insulate the entire loop except for the last 4 meters into the boiler drain.

Not for any safety reason. We typically dont install them and haven't had any trouble.

Mackin & Sons Plumbing thanks for the reply! So with no check valve, what prevents cold water from the bottom of the tank coming up the return line when you open the faucet?

@@joechristifano3990 a bit late, but, thermodynamics, cold water is heavier than hot, so hot water will always want to be at the top

You cannot use a check valve in this configuration. It will prevent gravity circulation. Best to use a ball valve or globe valve on the return to the tank and open it just a little. That way you will always have more hot water than the cooler water from the bottom of the tank going to the fixture. It will be negligible to the final temperature at the fixture. I am a 40 year red seal plumber in Canada One more thing. Don’t cheap out and use galvanized fittings to connect to the tank. They will internally corrode. Use brass fittings

@@paulnic7190 thanks for the input! I’m now leaning toward just installing a mini tank water heater under the sink. Bosch makes one for about $150. Seems easier than the return line.

You could but the shortest or most direct loop will probably work best. I'd be worried the longer loop wouldn't work very well.

@@wadsworthplumbers Thanks for the reply. So putting the return line at the first floor bath would not "short circuit" hot water getting up to the second floor?

@@greghanson8959 No it won't affect the other fixtures.

@@wadsworthplumbers Thank you very much for the guidance. Now, if only your service area extended to Texas... :-D

Noted

Yeah, sometimes a pump makes more sense but a gravity recirc works in most cases.