Insulate your lines. Pumps cost money to keep your water hot.

Thanks for your concern, but cost is not a problem. Currently, I’m wasting gallons of well water at the sink, and running my underground pump wastefully. All the lines are all in the ceilings of heating living space.

There was another recent thread on this subject, but I can't find it. It might have been on the KT forum--if I find it I'll add the link.

We installed one of the Bosch in-line heaters for the kitchen, so I could have hot water for the DW, even when the kids were taking showers. I really like it, but there is a learning curve. My unit has an automatic shut-off if the water flow is low enough that it would be heated to scalding temps. On the referenced thread I mentioned that my father's whole house in-line heater turns the unit off if that happens, and I have to go the laundry room to hit the reset button. On my unit the water just gets cold until I increase the flow.

Someone else mentioned that hard water deposits need to be flushed regularly, or the life of the unit is decreased. The unit needs a dedicated 220v/50amp breaker, and of course, water lines.

Found it--Kathsgarden posted the question in the KT. Tankless WH thread.

Recirculation pumps work great. I can absolutely recommend them. It made such a huge difference for our house.

But these pumps should be combined with the rest of the required infrastructure:

• pipe diameters should be sufficient to provide the required flow rate, but not more than that. Excessively big pipes can cause really long delays before you get hot water at your faucet. That was probably the biggest issue in our house. Easily had to wait for more than minute for warm water to get anywhere close to our bathroom, despite the fact that it was located right above the garage, where the water heater was. There was a lot of water trapped in those pipes.
• pipes should be insulated and should avoid exterior walls. You want hot water; you don't want a radiant heating system for your walls.
• things work much better if you have a dedicated return pipe for your recirculation system, as opposed to piggy-backing off of the cold water line. If you have more than one return pipe, make sure you balance the loads properly.
• the backflow valves in recirculation pumps are often inadequate. Install a separate backflow valve, or discover that your fancy new recirculation system keeps giving you cold water after all. Ask me how I know.
• recirculation pumps are frequently incompatible with tankless water heaters. Check your manufacturer's instructions, if you have a tankless unit.
• you should install a small expansion tank whenever you install a recirculation pump; it prevents possible damage to your pipes.
• consider a whole-house sediment filter. It'll make sure your pump lives longer.

@M has it right.

Circ pumps are reasonable in your situation but the pipes need to be insulated. You were a little too dismissive on that. You also need an insulated return line.

Thanks, Jake. Plumber said the pipes are hyper-insulated. The guy who custom built the house overdid everything. On steroids. (I’m surprised he didn’t have a solution in place for this issue, honestly.) But getting a dedicated return will be very hard if not impossible as the space is finished. I may have to do the Bosch booster. Sounds much easier.

Also, to clarify, I’m looking at under-sink boosters. The kind that run about $200 on Amazon.

Undersink booster are a mixed blessing. They tend to die every few years, they can spring leaks, and they are energy inefficient. But on the other hand, they are super easy to install and they are much cheaper than a "proper" solution. You can buy many boosters (and pay higher electrical bills) for the price of having your plumber add more pipes.

On the other hand, even in finished space, running new pipes isn't the end of the world. Plumbers do this all the time. A good plumber can do so with minimal required sheetrock repairs. So, it wouldn't hurt to get a couple of quotes before you give up on this option. We had some more gas and water pipes added over the years, and I was always surprised how relatively painless the process turned out.

If the pipes are insulated properly, the 4 gallons of cold down the drain should only happen at the initial start of meal preparation. Capture that in your pot for your pasta water and move on. The water will be warm for the rest of the kitchen use.

The cost of the “instant” solution in a finished kitchen far exceeds the 4 gallons of cold water down the drain at faucet start up. That’s both in initial startup costs for the added electrical circuit and in ongoing water and electrical costs. Unless you’re paying bottled water costs, this is a minor annoyance, not a critical issue. This should have been assessed and solved via traditional plumbing means at the rough plumbing stage of the remodel.

Hmm. Short-lived like a instahot tank, then? Been there. We have the further complication of hard water — which we do soften — but still. Thanks, all.