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gasman's avatar

Hot water recirculating system?

Asked by gasman (11315points) June 30th, 2010

I need some help choosing a hot water recirculation pump & related equipment for my home. Some of the plumbing in our house is over 100 years old & probably runs hundreds of feet through the house. (When I get up for work I turn on the shower then fix myself a cup of coffee while it heats up.) This seems to be the perfect application for a recirc system.

As luck has it the farthest hot water tap in the house (kitchen sink) is a straight shot of about 40 feet from the hot water tank along the basement ceiling, so I’ve already run insulated ½” copper tubing for a return line. Neither end is connected yet—one end is near the water heater & the other end is under the kitchen sink.

I know I’ll need an electric pump (I can tap into a 120V junction box near the water heater) and some sort of programmable timer. I’d rather have an external timer than one built into the pump.

I know I’ll also need a one-way check valve—or are those built into the pumps? Where do you put a shut-off? What kind of flow rate is needed? Do I secure the pump to a ceiling joist or just let it hang by the pipes?

Need suggestions from plumbers or experienced DIY-ers. I’m willing to spend a little more for something rugged & reliable. Online searches turn up so many products that it’s hard for me to evaluate. Thanks, Flutherites!

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5 Answers

lilikoi's avatar

Have you considered tankless hot water heaters?

gasman's avatar

Thanks—you’re not the first to suggest that. I suppose it makes a lot of sense in some situations. But my water heater is a modern 50-gal electrically heated tank that already gets plenty hot reasonably efficiently. The problem is the distance (measured in flow time) between hot water taps. I already use dishwashers with “added heat” but it’s out of the question to install a heater at every faucet (it would look really weird in our Victorian bathroom with clawfoot tub & pedestal sink).

Besides, I’ve already spent over $100 running pipe in the basement (half the cost for actual copper) & want to see this thing through. I think hw recircualtion makes an elegant system, especially using a return to create a true loop—there are systems that just shunt a little hot to cold. Plus I live in a climate where it’s usually heating season, so heat loss from hot water pipes won’t be such a bad thing. I knew I’d use a return pipe & that’s how I learned to solder copper. But I didn’t pick out a pump yet, then got to thinking about all these details I hadn’t thought of…

Like most of my DIY projects: Ready, Fire, Aim ~

kelly's avatar

we have a 50 gal natural gas with recirculating pump. Laing Model SMT 303 BTW, 1/150 hp, 3450rpm, 33 watt, 0.3 amp. it has a timer but we have it set for continuous running. It has been going since summer of 2005 with no problems. there is a sillcock next to unit in the exit line to “bleed’ air out of circulating loop. when power goes off or work on pumping sometimes we need to bleed so air is out to make system efficient.

gasman's avatar

Thanks for your answer @kelly Looks like one of those Laing pumps is just what I need & glad to hear yours has been reliable. I hadn’t even thought of a bleed valve for trapped air. Do you know if there’s a one-way valve in your system?

kelly's avatar

@gasman sorry for delayed reply, away from confuser. I do not know it there is a one way valve in the system, I don’t think so.

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