Plumbing for hot water recirc

[Jimongee]

Ok so ya'll have provided so much help so far that it seems like you should be sending a bill Or moving in!,
So another question; Same house...new construction. I am using PEX. I'm installing a gas 50 gal HW tank. This is a single floor 3500 sq ranch with a another bath in the bonus over the garage. i have not started the PEX install. That is today's plan. I want to incorporate a hot water recirc loop. I do not plan to use any manifolds...not a fan. I have done so much research on the best recirc system install for new construction and I'm still confused. Some of the diagrams connect the recir pump to the tank discharge spigot and create a continuous loop with branches to each fixture and return to tank. Yet other layouts recommend creating the loop but dumping the hot water after the farthest fixture into the cold line with a T to return to the tank. Seems logical hence putting warmer water back into the hot tank..allegedly saving gas to heat regular incoming cold water. In this layout the pump was placed at various locations in the loop...which confused me even more. If anyone can simplify this...that would be very appreciated.thanks
Jim in Franklin, TN

 

[phishfood]

Run the hot to the farthest fixture as normal. Tee into the hot line just before that fixture, and run an uninterrupted line back to the water heater. Put the pump at the water heater.

 

[Mr_David]

I found setting the pump low and into the bottom of the tank at the drain cock port works best. Sometimes a system connected like this will recirc even with out the pump. The reason for that can be a whole new discussion entirely.

When the water system gets shut off and restored, air gets in the system.
The higher the pump is installed the easier for it to get air locked and not move the water.

when the pump gets air in the line, the pump can NOT move the water.
If the pump is set low, that air can percolate up into the tank, keeping the water flowing with out having to manually flush the return line.

I always try to install a ball valve directly into the drain port, then a tee for the return line and a drain valve.. This way I can close the ball valve and use the drain cock to flush the return line.

Run the return line to the farthest fixture or fixture that will maximize the availability of hot water when needed If you run multiple lines the draw back will take the path of least resistance. The branch lines will then just draw from the hot main loop when needed.

I service an 3 story multi unit building that has 3 lines coming back to one pump. we have circuit setters ( glorified ball valves) to control the flow rate of each line. I have to manually flush the system every time we shut the building down or I will get the after hour call that someone is not getting any hot water.

A lot of large multi unit building with a parking garage below have the main Hot/Cold/Return making the big loop in the garage with risers going up 3 or 4 stories. None of the risers have returns.
Every one draws up from the main loop.

 

[Jimongee]

Hey thanks krazdav. I am probably a bit thick headed in these later years. Any chance you could do a little pencil diagram for me. I seem to comprehend the old "picture better than a 1000 words" best. Either way-thanks to all who helps me.
Jim

 

[KULTULZ]

Consider This-

Reference diagram. This is a CLOSED LOOP RETURN w/ DEDICATED RETURN LINE. The pump (and thermostat) are placed immediately after the last fixture in the hot water supply. This placement allows the pump only to draw hot water to that last fixture. It will cut the flow and you will not have to heat the entire loop back to the WH.

You should also install in the return loop close to the WH an air vent (also one way valve) to prevent air bubbles in circulation.

You can GOOGLE HOT WATER RE-CIRCULATION SYSTEMS for more info and illustrations.

The above is certainly open to debate...

 

[Jimongee]

Thank you kultulz! That is simplified and it makes sense. Just wondering; why do so many of the best other sites on the net recommend dumping the recirc hot loop back into the cold in at the tank?

 

[KULTULZ]

Just wondering; why do so many of the best other sites on the net recommend dumping the recirc hot loop back into the cold in at the tank?

Do you mean return to the COLD INLET at the top of the tank instead of bottom feed?

 

[frodo]

Thank you kultulz! That is simplified and it makes sense. Just wondering; why do so many of the best other sites on the net recommend dumping the recirc hot loop back into the cold in at the tank?

I guess, because they are not really the best site,


air collects at the top of the heater and will cause pump failure
air will not collect if pump is connected on the bottom.

 

[Jimongee]

Thanks. I think they hooked the hot loop return back into the cold in to in theory refil the tank with somewhat preheated water. No sure, but I have a neighbor who always seems to purchase top drawer building material and researched professional installer contractors. And that is how they installed his recirc system.

 

[frodo]

Thanks. I think they hooked the hot loop return back into the cold in to in theory refil the tank with somewhat preheated water. No sure, but I have a neighbor who always seems to purchase top drawer building material and researched professional installer contractors. And that is how they installed his recirc system.

makes no difference, a water heater has a dip tube on the cold water side that directs the incoming water to the bottom of the tank.

if you hook the circ line to the top,the water is piped to the bottom via the dip tube,

if you hook it to the bottom it is the same thing.

the only reason , imo, to install a pump on the bottom is to ensure longer pump life.

I have never in 30 plus years of plumbing using engineered drawings
have had an engineer draw the pump on the top.
i have always figured them boys with their computers, slide rulers and pretty secretaries just might know what they are doing.

 

[KULTULZ]

But...

If the pump is installed @ the bottom, it is subject to sediment(s) being drawn back into the loop and damaging the pump (plus the need for a vacuum relief valve).

Plus, bottom feed requires more plumbing and makes it more difficult to do a straight water heater replacement.

The below Ill shows the pump being installed @ the WH to prevent having to heat the entire return loop with a free standing aquastat @ the last fixture (requires additional wiring) and will still allow the heated water circulation to end there.

What concerns me is how the chosen manufacturers' pump is rated for push and/or draw and how much heat it is designed for.

 

[frodo]

Kultulz, to be honest, with the dip tube, i really do not see it makes any difference at all

I really think it comes down to convenience and accessibility of the installer.

with top feed and bottom feed, the dip tube puts the water at the bottom

it is the same thing

 

[KULTULZ]

Kultulz, to be honest, with the dip tube, i really do not see it makes any difference at all

I really think it comes down to convenience and accessibility of the installer.

with top feed and bottom feed, the dip tube puts the water at the bottom

it is the same thing

You're correct, the dip tube provides the same purpose. My concern is flow reversion out of the tank to the pump w bottom return.

Same as with a bottom feed WH install. Possible reversion, air bubbles and the need for a vent install.

 

[frodo]

You're correct, the dip tube provides the same purpose. My concern is flow reversion out of the tank to the pump w bottom return



not a concern, a check valve is required

 

[Jimongee]

Frodo...thank you,
Now I get it. That makes total sense! The returning how water ends up at the bottom of the tank either way. I wonder how many folks never really thought of that?! So one more thing. You mentioned the pump life is extended by installing it at the bottom. How does the install location influence the pump longevity? See that...your help is making me dangerous. Thanks again for the common sense explanation. Jim