New Home - Recirculating Hot Water

[sdkubota]

If the HW lines are in the basement ceiling and the HW heater is below them, IMO a pump is optional (and having dealt with pumps dieing in a hotel hot water recirculation system, I would prefer to avoid them).
Below is how my system is configured:
View attachment 283650

Aaron Z

I fail to see how the system you show would have any chance of working. The water pressure within all of those pipes is essentually equal and therefore not capable of opening any check valve allowing flow one way.

 

[aczlan]

I fail to see how the system you show would have any chance of working. The water pressure within all of those pipes is essentually equal and therefore not capable of opening any check valve allowing flow one way.

Hence the swing check valve. It has a flapper that swings open and shut (NOT spring loaded) so the water drifting past (as it cools down in the uninsulated pipe) will open it but it cant flow backwards.
That was the thing that the furnace guy stressed, it MUST be a swing check valve or the system will NOT work.
It works very well for us.

Aaron Z

 

[foggy1111]

Hence the swing check valve. It has a flapper that swings open and shut (NOT spring loaded) so the water drifting past (as it cools down in the uninsulated pipe) will open it but it cant flow backwards.
That was the thing that the furnace guy stressed, it MUST be a swing check valve or the system will NOT work.
It works very well for us.

Aaron Z

^^This is the type of system tha is being promoted for our new home. A plumber / friend told me this was the real deal. IF we have a circulating problem....then we could always add a circulating pump (doubtfull as our water heater is at the low point in our loop). Also the pump could be put on a timer to save electric. We will have our bathrooms, kitchen, and two laundry areas served by the hot water loop.....so this system sounds like a winner for our needs. Those instantaneous heaters may be good for sink purposes.....but I think the maintainence issues could be a problem over the long pull (?).

Thanks for the responses.

 

[BIG DOOLEY]

I took out my 40 gallon water heater in 2004.
I purchased this Bosch on-demand tankless heater and it has performed worry free since.
I located it between my kitchen and laundry area. there is hardly any wait time for hot water even when not being used for days.
but
at the bathroom and shower on the other end of the house there is a wait time to pass all the cold water in the crawl space out of the line to the bathroom.
my unit is a small water heater and is good for
1 shower
2 sinks
1 laundry
1 sink and dish washer
there is a gallon per minute limit as to how much water it can heat.
they make larger units that can handle a shower and sink at the same time.
we time our showers around the laundry time.
seven showers in a row without loosing hot water is nice.
if i had a basement i would install a second for the bathroom.
read up on them
in the coldest part of winter my inlet temerature can get down into the 30's deg f
im on city water but the lines were run too close to ground level. they don't freeze but get very cold.
we still have hot water but not scalding hot in the winter. in the summer i turn the temperature down.
there is no heating water all day long. no circulation lines or pumps.....
the newer units are electronic ignition and have a power vent option also for horizontal discharge i believe.
tom

View attachment 283675View attachment 283676View attachment 283677View attachment 283678View attachment 283679View attachment 283680View attachment 283681

 

[aczlan]

^^This is the type of system tha is being promoted for our new home. A plumber / friend told me this was the real deal. IF we have a circulating problem....then we could always add a circulating pump (doubtfull as our water heater is at the low point in our loop).

That is what our heating guy told us when he recommended that setup.
Cost was probably under $20 as I was going to insulate everything anyways, I re-used the shutoff valve and I had some extra PEX leftover (cheaper to buy a 100' roll than 40' by the foot).

Aaron Z

 

[aczlan]

I took out my 40 gallon water heater in 2004.
I purchased this Bosch on-demand tankless heater and it has performed worry free since.
I located it between my kitchen and laundry area. there is hardly any wait time for hot water even when not being used for days.
but at the bathroom and shower on the other end of the house there is a wait time to pass all the cold water in the crawl space out of the line to the bathroom.

We actually have 2 HW heaters, a ~40 gallon indirect one that runs off of the boiler and a on demand tankless electric one (44 amps at full load). When we use the indirect heater, the loop works well. When we use the on-demand heater it doesn't work. I have thought of adding a pump on a timer/temp sensor to keep the water at the sink hot at high use times, but that is as far as I have gotten.

Aaron Z

 

[sdkubota]

Hence the swing check valve. It has a flapper that swings open and shut (NOT spring loaded) so the water drifting past (as it cools down in the uninsulated pipe) will open it but it cant flow backwards.
That was the thing that the furnace guy stressed, it MUST be a swing check valve or the system will NOT work.
It works very well for us.

Aaron Z

I am still doubtfull about any valve working as there is zero pressure differential or in other words nothing to make the valve open and close. Perhaps even without any swing valve the cooler water would settle in the return line and head back towards the water heater. Perhaps this does work but many times what people think does not meet scientific reality. I would like to know why this isn't common knowledge in the plumbing industry as you have an almost perpetual motion machine.

 

[aczlan]

I am still doubtfull about any valve working as there is zero pressure differential or in other words nothing to make the valve open and close. Perhaps even without any swing valve the cooler water would settle in the return line and head back towards the water heater.

If you look at the valve, the flapper just swings back and forth. When I brought it home, it just rattled around

Perhaps this does work but many times what people think does not meet scientific reality. I would like to know why this isn't common knowledge in the plumbing industry as you have an almost perpetual motion machine.

Well, cold water falls, as water cools off, it drifts down the pipe and into the cold water input. I can feel the temperature differential on that vertical copper water pipe, MUCH cooler at the bottom than at the top.
The furnace guy has been working with boilers and furnaces since he was ~10 (according to his stories anyways) and really knows his stuff. He was the first person who could look at my system (wood boiler tied in with oil boiler) and tell me something that I didn't already know about it. If anyone in the area wants his number, I would be happy to pass it on.

Aaron Z

 

[KennyG]

When I remodeled our house a couple of years ago, the plumber added a thermosiphon line for the master bath. It is on the second floor on the opposite end of the house from the hot water heater in the basement. When you turn on the shower, you have hot water in less than 5 seconds. No pump, works like a charm. This is nothing new. I'm sure people have been installing these for over 50 years.

 

[vwnotrunning]

Piped properly, the gravity return or thermosiphon piping arrangement will work and alot of plumber install them. The check vavle is more to prevent the hot water from flowing backwards and allowing the piping to get warmer on the return side and causing the system to stop flowing. Many plumbers will not plan ahead far enough to install a working system or the owner / general contractor makes changes that will not allow the system to function properly. Pipe routing is critical.