Planning for installation of hot water recirculator

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phxphun

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Our kitchen sink is farthest from the heater and takes quite a while to get warm water to. We'd like to conserve all that wasted water, so have decided to add a hot water recirculator. There seems to be quite a large price range between models, so I'm wanting to get an understanding of what I need to considered before purchasing.

The house has a dedicated return line built-in, but the previous home owners had at some time removed the pump. We'll be installing the pump on a 50 gal GE Geospring Hybrid water heater we just installed.

My preference would be to have a pump that's going to last at least 8 years, is as energy efficient as possible, and provides instant hot water at the kitchen sink (of course). It would also be nice if the installation were as simple as possible.

My questions are:
Is it better to install the pump on the dedicated return line (pumping the returned water into the drain at the bottom of the water heater). Or is there an advantage to the type that attaches to the hot water line at top of the heater and requires a 'bypass connection' installed between the hot and cold lines at the furthest point of use in the house. (We see a model at the big box stores for $200).

There are various flow rates across different models. Is pump capacity something that needs to be considered?

Any tips or experience shared would be greatly appreciated.
 

hj

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If you actually have a "functional" dedicated circulation line, you would NOT want the "retrofit" system that mounts on top of the heater. You actually want the "smallest" pump you can find, and even then you may have to reduce its flow so it just keeps the line hot without causing erosion in the piping.
 

WJcandee

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You already have a dedicated return line. The Grundfos (or Watts -- it's the same stuff) Comfort System that rolls it over into the cold water line is for homes that don't have the return line already installed. We have that and it's great, but if you have the return lines already installed, by all means use them!

Here's a piece from Grundfos that explains it better. http://us.grundfos.com/products/fin.../LUPSL021_UP10-16 Sales Flyer_3-12_Lo-Res.pdf

At some level, however, the simplest, easiest, most reliable method is just to install the pump at the hot water heater and run it all the time. That's what we do. This will mean that you always have quick hot water at the tap. Not instant, because the recirc loop is still a couple of feet away from the faucet. But within a period of a couple of seconds, it's gonna be HOT.

The pump doesn't use a meaningful amount of energy, but recirculating the water constantly will result in some temp loss that wouldn't occur if it were just sitting in the hot water heater, so there may or may not be a meaningful change in energy consumption if you just run it all the time. To maybe save some energy, you have two options: (1) timer and/or (2) aquastat. The thing will only circulate the water during certain times of day or when the temp at the end of the line goes below a certain level. Of course, there is then some time lag between the pump turning on and the hot water filling the loop. If you have just one loop, you can easily install a Grundfos pump at the end of the loop and tweak it till you get it the way you want. If you have more than one loop (as we do), then you need one pump per loop unless you install it at the hot water heater. The Grundfos one in the piece goes by the water heater where the return line enters the heater.

So those are really your decision criteria. As to brands, the Grundfos seems to be one that the plumbers around here, at least, use and recommend. There are multiple channels in which you can purchase it. I usually stay away from the Big Box on this stuff; local plumbing supply or online is where I would look. Because you are actually looking for the smallest pump that will keep the loop hot in the winter -- and it doesn't take much, interestingly-enough, you really aren't looking at anything that's going to use a lot of juice.
 
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Jadnashua

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The install also needs a checkvalve, otherwise, when you turn on the hot, you may be drawing it from both the top (hot) and bottom (could be colder) ends of the waterheater. SOme pumps have a built-in check valve. For potable water, the pump must be either bronze or SS...IOW, you cannot use one designed for heating purposes - the dissolved oxygen in the water will quickly eat the impeller away.
 

WJcandee

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To Jim's point, the Grudfos one in the material I linked to has a built-in check valve for exactly the reason that Jim mentions.
 

hj

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ALL check valves will fail, so I would prefer a separate one, rather than in a pump where you might have to buy a new pump to get proper operation again.
 

Reach4

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ALL check valves will fail, so I would prefer a separate one, rather than in a pump where you might have to buy a new pump to get proper operation again.
What would be the symptom of a failed check valve in a recirc system?
 

Jadziedzic

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Look into the Laing (or Bell & Gossett) "ecocirc" models - very energy efficient, and has options for either (or both) thermostatically-controlled operation and a timer to run during certain hours.

You won't find these at the box store, but it's worth the effort to find an online supplier.
 

phxphun

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Thanks everyone for the great feedback. I think I've got an idea of what I need now.

wjcandee - Thanks for the Grundfos link and explanation of things to consider. I'm now planning on the UP10-16BU ATLC because it has all the bells-and-whistles (we'll probably benefit from the timer), including an aquastat and built-in check-valve (it appears the other models don't come with a check-valve).

Will this model have the capacity for a 3100 sf house? Also, it comes with an 1 1/4" Union for installation. I assume, with the right fitting, I can install that onto my 3/4" return line. Correct?

hj - How would I know if the check-valve failed? Less-immediate hot water, I imagine.


jadziedzic - Thanks for the Laing suggestion. I was initially planning on the Laing Thermotech E3-BCSVNN3W-11, but when I read the instruction manual it said these pumps are not for potable water. (The Autocirc models, which don't have this warning, are for under-sink non-dedicated line installations).
 
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