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Old 05-08-2012, 09:33 AM   #1
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Hot Water Recirc?

I posted the below in a thread by Daluu regarding hot water solutions....this really should be it's own thread....and yes...I did search....

I'm in the middle of a 2-story addition....part of the project involves moving my water heater from the front corner of the house to the back/side of the real world means that hot water will be about 20' closer to the majority of items that use it...but it also means that the kitchen (front of the house) will now be about 30' (as the pipe fly's) from the water heater. Add to that the new upstairs bathroom....delay in getting hot water is going to be an issue......hence, I'm looking at hot water recirc systems.

I have ruled out the simpler system that uses the cold side as the return...when I want cold water...I want cold water....seems counter productive to have to waste water on the cold side while you wait for it to get cold. In other words, goose pretty much covered the issues.... looks like I'll go with a pump (on a timer) with dedicated return line....

Hence...the question....does the return line need to be 1/2" or 3/4"? Any reason I can't use 1/4" or 3/8"? I realize that the pump would need to run a little longer to get the lines heated up....but, if I can use 1/4"...then it means I can use 1/4" tubing which comes in nice long rolls....which means less sweat connections....easy to route....etc.

Side note....everything is/will be insulated.


Even if you are on the right track, you will still get run over if you just sit there.

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Old 05-08-2012, 09:45 AM   #2
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Pump connections are usually standard 3/4" or 1/2"

Reducing the line size too small may reduce the pump's ability to overcome any head pressure, but to be sure on that, it would be better to call the manufacturer of the pump you intend on installing.

We typically use 1/2" unless we're picking up a fixture or two on the other side of the loop in which case we bump it up to 3/4"


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Old 05-08-2012, 09:08 PM   #3
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Go with the third line ˝ inch return, use a timer for peak hours of operation and an aqua stat for temperature control while in operation saves pump life and electrical operation cost. Insulation on the return is a must for peak efficiency. Depending on the plumbing layout system may need to be split to operate properly.

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Old 05-08-2012, 09:23 PM   #4
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i to agree with adding return line in commercial due to lot of use and knowledge of turning pump on but in residential there are some rec. that have a temp sensor in them so it just puts cold water in cold line but you have to push button or use occupancy sensor.
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Old 05-09-2012, 08:12 AM   #5
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I am using the Grundfos UP10-16BU/ATLC. Very nice pump with aquastat and timer. You mentioned a large roll. I assume you are referring to flexible copper. I am sure you have your reasons, but why not PEX?
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Old 05-09-2012, 12:31 PM   #6
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Originally Posted by yogi_bear_79 View Post
You mentioned a large roll. I assume you are referring to flexible copper. I am sure you have your reasons, but why not PEX?
+1 Using PEX would be easier than using copper.

I assume you already have copper lines in your home in the trunk & branch configuration. If so, if you do use PEX for your return line, suggest that you use the same size PEX tubing as your copper trunk line(s) since the inside diameter of PEX tubing is smaller than the equivalent size copper pipe.

Assume that you have 3/4" copper trunk lines now. The ID of the copper trunk lines will be 3/4". However, the ID of 3/4" PEX tubing is 5/8". --- Now if you use the crimp or cinch system for your fitting connections, the ID of the fittings will be even smaller, probably about 1/2". --- If you use the Wirsbo/Uponor PEX system that uses the expansion method for fittings, the ID of the fittings will be about 5/8" so there will not be any flow restrictions introduced by the fittings.

Although 3/4" PEX tubing appears to be fairly stiff, it's actually quite easy to pull and run 3/4" PEX tubing off a long roll. No fittings needed except at the ends that connect to your plumbing system. However PEX tubing must be shielded from direct or indirect sunlight so if that's not possible for you, then forget about using PEX.



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