3rd line(loop) for instant hot water for sinks.

Hello. I have a typical small 1 story 3 bed ranch(approx 1300sqft) with full basement. I want instant hot water to my 2 bathroom sinks and kitchen sink and I am wondering which way would be cheaper to have running after install costs vs electric under sink instahot or if any of them are even worth it. Its an unfinished basement with exposed pex that I actually piped out when home was purchased along with boiler.

So I was thinking of running a 3rd line off bottom of indirect hot water heater with a circulator pump and tie it in at the end of the existing hot water feed where it supplies the last sink. Obviously it would be constantly circulating and I am wondering:

1) I know there are a lot of factors, but would running hot water through a 3rd loop constantly so it is available on demand be any cheaper as opposed to someone washing there hands for a minute with the hot water faucet on and draining all that hot water out of hot water heater and then turning it off before the hot water even got there?

2) Is the 3rd loop method cheaper to run after install than an electric instahot under sink after install?

in my opinion.
it is all in the wiring,are you familiar with a 3 way switch?
install an extra wire [runner] from bathroom to bathroom
the pull a wire from one bathroom to the pump.
install 2 ,,3 way switchs in the bathroom to control the light and the pump
when you walk into the room and turn on the light the pump also kicks on
when you turn off the light the pump also turns off the lpump

install a regular switch at the kitchen

consult a licensed electrification for the wiring

You can use a Grundfros comfort system with out a 3rd line, but seeing you have easy access to run a 3rd line, 3rd line would be more feasible if done with PEX.

You can add a remote switch to turn on pump or a timer like one used for Christmas tree lights, or a pump with a timer.

Grundfros makes a good pump.

Comfort system pump goes right on the hot outlet on the water heater with a special block valve that control temp flow.
picture below show pump at sink

Grundfros Comfort System.PDF

3rd loop is way way less expensive, a good insta hot unit is $500.0
you are talking about 3 of them $1500.00 lotta cabbage

frodo said:

in my opinion.
it is all in the wiring,are you familiar with a 3 way switch?
install an extra wire [runner] from bathroom to bathroom
the pull a wire from one bathroom to the pump.
install 2 ,,3 way switchs in the bathroom to control the light and the pump
when you walk into the room and turn on the light the pump also kicks on
when you turn off the light the pump also turns off the lpump

install a regular switch at the kitchen

consult a licensed electrification for the wiring

View attachment 15268

Click to expand...

That's actually a great idea. I think I might do that but I don't understand the significance of running wire between baths and installing 3way switches. I would want each switch to operate the pump independently. Also you need to make sure all switch wiring is on the same phase or else you will fry a 120v pump if two switches that are on different phases are on at the same time(240v going to pump is no good).

So can anyone answer my original questions?

JohnDS said:

That's actually a great idea. I think I might do that but I don't understand the significance of running wire between baths and installing 3way switches. I would want each switch to operate the pump independently. Also you need to make sure all switch wiring is on the same phase or else you will fry a 120v pump if two switches that are on different phases are on at the same time(240v going to pump is no good).

So can anyone answer my questions?

Click to expand...

not me, consult a licensed sparky for wiring

I was referring to my original questions lol.

instead of using a 3 way switch you can install a switch with a motion sensor
in each bathroom, and kitchen, but you will have to install some type of relay switch
at the pump

Years ago I built a home in Michigan with a full unfinished basement. I ran a 1" copper trunk line for all hot and cold water. (We never got scalded when someone flushed while we were in the shower) The water heater was at one end of the house and the two bathrooms were at the other. I tee'd into the 1" at the bathroom end with 1/2" copper with a check valve and ran back to the heater. I plumbed the 1/2" into the bottom drain of the heater and the water gravity circulated because of the temperature difference. No pump was needed and we had instant hot at the bathrooms. DO NOT forget to insulate the 1" hot and the 1/2" return line. Or you will be heating your basement with the water heater.

That is a good idea . if the WH is in the basement, the hot supply is always rising toward the fixtures and the 3rd return line is falling toward the WH a gravity recirc system can work. No pump required.


In regards to frying a 120v motor with a double fed circuit.
to get 240 volt both leads have to be 120.
So if you fed the motor from 2 different breakers. one hot lead from both breakers to the same terminal on motor and a common (ground), the voltage would still only be 120 to motor. but you would have to make sure you turned both breakers off to work on it and you would also loose the protection of the breakers from tripping if one of the lines shorted out or was overloaded.

I'll say it another way
For the voltage to be 240 you need 2 breakers, the difference is one breaker is connected to 1 terminal on the motor and the other breaker is connected to the other terminal. NO common wire connection. maybe a green ground.

If you are talking cost of just running the water and paying for that or paying for the cost of powering a pump, that would require stats on pump power usage, water cost and how much is wasted while waiting for it to get hot, and a lot of math and experimentation. And also the abundance of available water to waste.

I have been kicking this around and have come to the conclusion that a 24 low voltage
system would be the way to go.
using a 24 volt motion sensor
and a relay at the pump