# Please tell me about home hot water recirculating pumps (for instant hot water) **URL:** \ **Category:** In My Humble Opinion\ **Created:** [January 14, 2023, 9:42pm UTC](https://boards.straightdope.com/t/please-tell-me-about-home-hot-water-recirculating-pumps-for-instant-hot-water/978238 "2023-01-14T21:42:48Z")\ **Posts on this page:** 13\ **Page:** 1
**Author:** ![hajario](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/hajario/32/171_2.png) [@hajario](https://boards.straightdope.com/u/hajario)\ **Post date:** [January 14, 2023, 9:42pm UTC](https://boards.straightdope.com/t/please-tell-me-about-home-hot-water-recirculating-pumps-for-instant-hot-water/978238/1 "2023-01-14T21:42:48Z")
I hate having to wait for hot water especially because it wastes water in my ordinarily drought stricken area. This seems like a great solution. Is it? What are the pitfalls? If it matters, my house is on a raised foundation and the plumbing is all upgraded to copper. ---
**Author:** ![LSLGuy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lslguy/32/5813_2.png) [@LSLGuy](https://boards.straightdope.com/u/LSLGuy)\ **Post date:** [January 14, 2023, 9:54pm UTC](https://boards.straightdope.com/t/please-tell-me-about-home-hot-water-recirculating-pumps-for-instant-hot-water/978238/2 "2023-01-14T21:54:31Z")
Here’s an excerpt from a fairly recent post of mine wherein I evangelized about the system I got about 10 years ago. > [@Modern device your parents had that you don’t have now](https://boards.straightdope.com/t/modern-device-your-parents-had-that-you-don-t-have-now/970470/12): > > Instant whole-house hot water can be retrofitted easily & inexpensively to any house with no significant plumbing required. I did it to my former McMansion with looong slooow hot water runs a few years ago. This is what you’re looking for: > > **[https://www.amazon.com/dp/B000E78XHG](https://www.amazon.com/dp/B000E78XHG)** > > The black plastic fitting goes under the sink at the end of each run, so perhaps install one device per bathroom, one for the kitchen, and maybe one for the laundry room. It’s a mechanical thermostat valve that interconnects the hot & cold side pipes. It installs past the angle stops and before the lines to the sink faucet. The single pump is installed in the HWH outlet line near the HWH. > > The basic idea is the pump provides a small pressure head so the downstream hot water supply is pressurized vs the cold supply. And the remote thermostats are closed when the hot water supply is hot enough but open a connection between the hot & cold supply when the hot side is only warm-ish. > > The net effect is when the sink supply is receiving only warm-ish water the valve opens, the pump pushes fresh hot water from the HWH down the line while the used-to-be-hot water in the hot-side pipes returns backwards up the cold-side supply line towards the house inlet where it then returns to the cold side of the HWH. No water is lost. > > You can configure the timer on the pump to only run certain times of day so there’s zero energy consumption moving water around and reheating it during the times of day or night there’s no need. Couple that with insulating the accessible portions of your hot supply pipes and you get almost instant hot water anywhere / everywhere in your house for very little installation cost or difficulty and negligible operating cost. I would totally do that again if I lived in a single-family house or even a condo with long enough pipe runs. I’m not endorsing that brand and model specifically, but just that general concept of a recirc system. The biggest concern for you is whether you can adequately insulate the hot water lines. If your lines were embedded in a slab, then insulation is out of the question and the operating cost would be noticeably high. Conversely, most of my runs were along the exposed joists in the unfinished basement. So in a semi-climate controlled area and readily accessible to slip foam sleeves over the majority of the hot water line runs. In my case the operating cost was truly negligible even if the pump was active 24/7/365. The result is not “instant” hot water, but it’s warm in 5 seconds and hot in 10 seconds even 100 feet from the HWH. Magic I tells 'ya! Here’s a quote of another poster in another thread with cites to potentially useful articles. > [@Can I Do This Electrical Thing-Water Heater Recirculating Pump](https://boards.straightdope.com/t/can-i-do-this-electrical-thing-water-heater-recirculating-pump/975821/13): > > There is a special device that hooks to the hot and cold taps at the farthest faucet. Inside that is a temperature-sensitive device that is open when the water on both sides of it are cold. On demand, or on a timer, the recirculating pump sends hot water through the hot water line, to this valve, and then forces it back on the cold water line. It does this until the temperature valve senses that hot water is now available at the faucet. At this point the valve closes, leaving hot water at the ho… I’ll also point out that in the part of my post I did not excerpt I mention another handy hot water gizmo: truly instant near-boiling water for your kitchen sink. Super handy for cooking, making tea, etc. Not useful for washing. If that might be of interest to you, check out the rest of my earlier post. ---
**Author:** ![Chefguy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chefguy/32/138_2.png) [@Chefguy](https://boards.straightdope.com/u/Chefguy)\ **Post date:** [January 14, 2023, 10:11pm UTC](https://boards.straightdope.com/t/please-tell-me-about-home-hot-water-recirculating-pumps-for-instant-hot-water/978238/3 "2023-01-14T22:11:21Z")
I talked to a plumber about that for our former home. He said it wasn’t practical for a house like ours and would require a lot of rework of the existing plumbing. We had an on-demand tankless water heater installed, which, while not instantaneous, was continuous for as long as you wanted it. Plus no danger of it flooding the basement. ---
**Author:** ![hajario](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/hajario/32/171_2.png) [@hajario](https://boards.straightdope.com/u/hajario)\ **Post date:** [January 14, 2023, 10:43pm UTC](https://boards.straightdope.com/t/please-tell-me-about-home-hot-water-recirculating-pumps-for-instant-hot-water/978238/4 "2023-01-14T22:43:59Z")
Thanks for the great information so far. My standard hot water heater is in a closet. I’m in Santa Barbara so no basement and the pipes are under the house and it rarely gets very cold here. ---
**Author:** ![LSLGuy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lslguy/32/5813_2.png) [@LSLGuy](https://boards.straightdope.com/u/LSLGuy)\ **Post date:** [January 14, 2023, 10:54pm UTC](https://boards.straightdope.com/t/please-tell-me-about-home-hot-water-recirculating-pumps-for-instant-hot-water/978238/5 "2023-01-14T22:54:50Z")
If the crawlspace is accessible then insulating much of the pipe runs should be an unpleasant but doable task. ---
**Author:** ![China\_Guy](https://avatars.discourse-cdn.com/v4/letter/c/779978/32.png) [@China\_Guy](https://boards.straightdope.com/u/China_Guy)\ **Post date:** [January 15, 2023, 4:38am UTC](https://boards.straightdope.com/t/please-tell-me-about-home-hot-water-recirculating-pumps-for-instant-hot-water/978238/6 "2023-01-15T04:38:44Z")
We have this in Seattle. Built new 10 years ago. It’s great. We have two hot water tanks (mainly as a safety issue for my youngest so the hotest water would never scald her). When our re-circ system went out about 6 months ago, I forgot how good it was to have almost instantly hot water. I mean it takes a few seconds for the hot water to come out of the tap instead of what seems like a minute or two. ---
**Author:** ![Sam\_Stone](https://avatars.discourse-cdn.com/v4/letter/s/ecccb3/32.png) [@Sam\_Stone](https://boards.straightdope.com/u/Sam_Stone)\ **Post date:** [January 16, 2023, 2:49am UTC](https://boards.straightdope.com/t/please-tell-me-about-home-hot-water-recirculating-pumps-for-instant-hot-water/978238/7 "2023-01-16T02:49:29Z")
Or, for a couple hundred bucks you can get a small instant heater mounted under your sink. We had one of those in our old house, and it was hot enough that you could make tea or coffee with it. Basically a mini tankless water heater. ---
**Author:** ![hajario](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/hajario/32/171_2.png) [@hajario](https://boards.straightdope.com/u/hajario)\ **Post date:** [January 16, 2023, 5:08am UTC](https://boards.straightdope.com/t/please-tell-me-about-home-hot-water-recirculating-pumps-for-instant-hot-water/978238/8 "2023-01-16T05:08:11Z")
That was what I originally wanted just for the kitchen. I am about to embark on a kitchen remodel and that was going to be part of it. The contractor suggested a recirculating pump so I’d get the benefit for the whole house. This sent me down the rabbit hole. As it happens, a friend of mine just moved to town and has been a licensed plumber for a couple of decades. He is building up his clientele and has some free time. He will give me a deal on the installation. What under sink model would you recommend. ---
**Author:** ![pullin](https://avatars.discourse-cdn.com/v4/letter/p/c57346/32.png) [@pullin](https://boards.straightdope.com/u/pullin)\ **Post date:** [January 16, 2023, 12:56pm UTC](https://boards.straightdope.com/t/please-tell-me-about-home-hot-water-recirculating-pumps-for-instant-hot-water/978238/9 "2023-01-16T12:56:52Z")
My parents’ house has this, and it was wonderful. But it didn’t work well with on-demand tankless heaters. They tried this and ended up with a multi-year problem of wild temperature swings and repeated replacements of the tankless heater by the contractor. In the end they had to choose between replacing the tankless heater with an old-fashioned kind, or removing most of the re-circulation system. Dad chose the latter since their bathroom is located directly over the tankless heater. They just endure the 4 minute wait for hot water at the kitchen now (other end of large house). ---
**Author:** ![LSLGuy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lslguy/32/5813_2.png) [@LSLGuy](https://boards.straightdope.com/u/LSLGuy)\ **Post date:** [January 16, 2023, 3:10pm UTC](https://boards.straightdope.com/t/please-tell-me-about-home-hot-water-recirculating-pumps-for-instant-hot-water/978238/10 "2023-01-16T15:10:02Z")
> [@hajario](#): > > What under sink model would you recommend. The brand I’ve used is: > **[Instant Hot Water Dispenser - Hot Water Dispenser for Faucets & Sinks |...](https://insinkerator.emerson.com/en-us/insinkerator-products/water-dispensers)** > > An Instant Hot Water Dispenser is a Convenient Addition to any Kitchen. Learn More About Instant Hot Water Heaters and Find the Perfect Hot Water Dispenser. Note it’s NOT for instant hot water to your main faucet. It’s only for near-boiling water at a lowish flow rate for a quart-ish of volume delivered by a dedicated mini-spigot. I can recommend this brand as solid and dependable. You will want a fresh electrical circuit run under the sink to power it. ---
**Author:** ![Digital\_is\_the\_new\_Analog](https://avatars.discourse-cdn.com/v4/letter/d/a88e4f/32.png) [@Digital\_is\_the\_new\_Analog](https://boards.straightdope.com/u/Digital_is_the_new_Analog)\ **Post date:** [January 16, 2023, 3:43pm UTC](https://boards.straightdope.com/t/please-tell-me-about-home-hot-water-recirculating-pumps-for-instant-hot-water/978238/11 "2023-01-16T15:43:07Z")
I have a [Quick&Hot](https://www.amazon.com/Anaheim-AH-1300-Quick-Instant-Water/dp/B005OIGOK8) unit in my kitchen, installed about 10 years ago. I use it for tea, and used to use it for my French Press coffee. It’s also great for a quick clean of a utensil 😃 I love it. ---
**Author:** ![puzzlegal](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/puzzlegal/32/3827_2.png) [@puzzlegal](https://boards.straightdope.com/u/puzzlegal)\ **Post date:** [January 16, 2023, 3:59pm UTC](https://boards.straightdope.com/t/please-tell-me-about-home-hot-water-recirculating-pumps-for-instant-hot-water/978238/12 "2023-01-16T15:59:55Z")
My mother had an instant hot tap in her kitchen sink for decades, in two different homes. I can’t recall either ever giving her any problems, or needing to be replaced. I think she mostly used it for tea and making instant oatmeal and similar “I want a little bit of very hot water right now” uses. ---
**Author:** ![Sam\_Stone](https://avatars.discourse-cdn.com/v4/letter/s/ecccb3/32.png) [@Sam\_Stone](https://boards.straightdope.com/u/Sam_Stone)\ **Post date:** [January 16, 2023, 4:53pm UTC](https://boards.straightdope.com/t/please-tell-me-about-home-hot-water-recirculating-pumps-for-instant-hot-water/978238/13 "2023-01-16T16:53:10Z")
> [@hajario](#): > > What under sink model would you recommend. Sorry, I don’t know enough to give a reasonable answer. We had one in our first house 30 years ago and loved it, but haven’t had one since.