Installed a hot water recirculator

Project by Dan Lyke posted 04-03-2008 09:32 PM 5286 views 2 times favorited 9 comments Add to Favorites Watch

The tag line says “showcase your project”, and I’m not sure that plunking down a couple o’ Franklins and spending half an hour trying to untangle myself from Teflon tape really counts as a project that needs showcasing (especially since I ended up using paste rather than tape on the connections…), but at least one friend has asked about the hot water recirculator, so here’s a little rambling on hot water recirculators, and the one we ended up installing.

We have a tiny little house. It’s intentional, we want something where maintenance is easy, there’s just two of us, and though I work from home and we like having a futon for guests, we live in a climate where we can use the back yard for entertaining, and our hobbies at this point are riding bicycles and woodworking, so cozy wins. However, even with that tiny little space, and even though the bathroom plumbing and kitchen plumbing share a wall, it seemed like the hot water took forever to get to the bathtub. Furthermore, we live in an area where water isn’t unlimited, and we like to be conscious of conservation.

Enter the hot water recirculator: The purpose of this little beastie is to pull water from your hot water tank through the plumbing, and return the water to the tank, until the water is hot somewhere very close to the faucet. This used to mean running yet another return line back to the hot water heater, but someone figured out that on simple residential systems you can do this by just pushing the (formerly hot) water back into the cold water line.

There are two types of such systems: Some put the pump at the hot water heater and a simple mechanical valve actuated by a bimetal at the far end, and some put the pump at the far end.

The advantages of the former type are that they’re cheap, and that if you’ve got a branch line (like two bathrooms at opposite ends of the house) the valve for the extra line is super cheap. So we were initially tempted by those systems, but we came up against two potential problems:

1. If you run the cold water elsewhere, say to water the lawn or flushing the toilet, the valve is open ‘til hot water gets to it, so the process of watering the lawn causes the hot water to get primed to your valves, which means that much more hot water gets heated every time you use the cold water.

2. We don’t keep regular enough hours to turn this device on and off with a timer, so we wanted a button that said “I’ll want hot water soon”. Since our usage points are far away from the hot water heater, switching that pump on and off started to become a big hassle.

Thus we went with the Metlund D'<mand>. It’s small enough that it won’t punch holes in our 50 year old galvanized steel pipes before we have a chance to replace ‘em, it comes with a wireless option, so we didn’t even have to drill a hole to put a button in the kitchen, let alone one in the bedroom, and installation was dead simple.

The left picture is the pump sitting inside the bathroom vanity. Surprisingly, it it didn’t have good mounting holes, and it’s sitting on a piece of foam because otherwise that vanity acts as a sounding box. With the foam, it’s hard to tell if it’s on.

The middle picture is the hoses run to “T”s up near the faucet. This is not the recommended installation method, it comes with fittings for copper pipe to fit before the valves, but I was nervous about unscrewing the valve from the galvanized steel pipe and possibly inadvertently unscrewing parts further back in the wall: No reason for a half hour job to become an all day re-plumbing nightmare.

The right picture is one of the remote switches (we got two) double-sticky taped to the cabinets in the kitchen. The other one sits beside the bed, so when the alarm light goes on (yeah, we’re weird, our “alarm” is a big bank of daylight balanced flourescents) we can mash the button, wake up slowly, and by the time we stumble into the bathroom the shower is warm. It’s also trivial to run wired switches, we’ve got one on the side of the vanity now, and will be incorporating that into the design of the vanity we’re building.

Furthermore, for those extended soaking baths, heating up the water doesn’t mean running a lot of cold water first, just mash the button, wait a minute, and viola! Errr… wait, that’s not right, stringed instruments have nothing to do with this…

Probably not economically justifiable from a “water saved” standpoint, but sure is convenient! Just takes a 3 prong socket and a few minutes.

-- Dan Lyke, Petaluma California, http://www.flutterby.net/

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Dan Lyke

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bathroom kitchen plumbing parts

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9 comments so far

View MsDebbieP's profile


628 posts in 5558 days

posted 04-04-2008 01:21 AM

very interesting.
Sure sounds like a project worth showcasing.

-- ~ Debbie, Ontario Canada

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Dick, & Barb Cain

121 posts in 5553 days

posted 04-04-2008 06:10 AM

Sounds good, but isn’t there a way of putting a check valve in to prevent priming the cold water?

-- ** Dick, & Barb Cain *************** http://lumberjocks.com/jocks/Chipncut

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Dan Lyke

331 posts in 5544 days

posted 04-04-2008 04:06 PM

Since you want to allow flow from the hot side to the cold side, at least when you’re priming the hot water system, I can’t see how a check valve would work. Part of the appeal to us of the active pump system at the far end of the loop was that it wouldn’t let water flow freely from one side to the other when it wasn’t actively trying to pump it.

-- Dan Lyke, Petaluma California, http://www.flutterby.net/

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Dick, & Barb Cain

121 posts in 5553 days

posted 04-04-2008 04:35 PM

Thanks, I get the message.

-- ** Dick, & Barb Cain *************** http://lumberjocks.com/jocks/Chipncut

View PaddyO's profile


1 post in 5509 days

posted 05-08-2008 06:18 AM

I recently completed a similar project, but I used the circulating pump at the hot water tank and two thermal valves at the ends of my hot water lines. The pump is made by Laing. The original thermal valve was terribly noisy (vibrations & moans), but Laing sent me a warranty replacement that works much better. Later, I added the second thermal valve after I discovered how convenient it was to have hot water almost instantly for my morning shower. I used a competitor’s thermal valve for the second location because Laing couldn’t supply me with one due to an injunction related to patent issues. Both thermal valves now work consistently and quietly. The household schedules are fairly regular so the circulating pump is actuated by a timer. We typically use hot water at the branch-end locations only in the mornings and before retiring at night. I know we’re using much less water for daily showers, etc. because now we don’t have to turn on the hot water spigot for 1 to 1 1/2 minutes (wasted water down the drain) before the truly hot water arrives at the shower/lavatory from the hot water tank. Where I live, the water/sewer rates have tripled in the last 5 years, so I enjoy any dollar savings made possible by the recirculating system as well as the convenience.

Thanks for show-casing your project!

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Dan Lyke

331 posts in 5544 days

posted 05-08-2008 09:10 PM

PaddyO, thanks for the notes on your experiences! Oddly, our sewer prices are set by our water uses in the winter months (our rainy season), which means, in effect, that water during the time when we’ve got excesses of it costs us 3x as much as it does during the dry season. We’ve been looking at various graywater systems, but reuse for irrigation doesn’t help us during that period.

A month later, the instant hot water thing continues to be very cool, and I’ve finally broken myself of the “turn on the tub, go do something else, come back and see if the water’s hot” pattern.

-- Dan Lyke, Petaluma California, http://www.flutterby.net/

View sumppumpadvisor's profile


2 posts in 2036 days

posted 11-10-2017 08:17 PM

If you are looking for best hot water recirculating pumps then check out our guide at http://www.sumppumpadvisor.com/best-hot-water-recirculating-pump/

-- Sump Pump Advisor

View MarioK's profile


2 posts in 1758 days

posted 11-06-2018 02:19 PM

I try to do this project but I have to study more to finish it, maybe after read some comments I know why I can’t conclude

thanks, if you want to see my project just click here

View dwyane's profile


7 posts in 1745 days

posted 05-30-2022 04:31 AM

The concept you have done for Installing the hot water recirculator is good and I have seen the other projects done by you the interesting part is that nothing repetition is seen in your work which makes it an excellent concept when compared with the others work Lab grown diamonds

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