Plumbing for hot water

In my old house, getting hot water in the bathroom upstairs took a long time. I presume that best practices is to split the pipe from the water heater and send one pipe directly to the upstairs bathroom so you can have a nice shower, one pipe goes to the kitchen and from there. I think that my old house had like one pipe that went all around, which might save on buying pipe but is annoying for getting hot water where you want when you want it. This is silly, but my sweetheart and I disagree on which way is good to plumb the house. They are a contractor and I am not so I probably will be proven wrong. What’s the word?

That depends entirely on the layout of your house. Where is the heater, where are the bathrooms and kitchen in relation to the heater and each other. Where is it easiest to add new pipes.

Are you actually intending to do something about it or is this just discussion? If you want to do something about it, they do make something that can be easily retrofitted into existing plumbing. In the problem bathroom, you connect the hot and cold pipes (under the sink, typically) via a small pump. A few minutes before you’re ready to take a shower, you flip the pump on and it takes all the [not hot] water from the hot side and pumps it into the cold side bringing the hot water up to the bathroom.
Granted, it fills the cold plumbing with luke-warm water, but that should be purged as soon as you turn the shower on.
I’ve seen these done with a button/switch to turn it on. A timer to get it running right around the time you usually take a shower and even a remote you can keep in the area that you’re typically in before taking a shower (ie bedroom, kitchen etc).

And, yes, I know it doesn’t seem like you should be able to pump water from the hot water pipe into the cold water pipe, but you can since the water is just going around in a circle.
https://www.amazon.com/Watts-500800-Instant-Recirculating-Install/dp/B000E78XHG

The best piping system is a 3 pipe system. cold, hot, and hot return. My water heater is n the garage the kitchen and upstairs bathrooms are on the opposite corner of the house. It use to take running about 2.5 gallons of water before getting hot water to the upstairs bathrooms. When I added on to my wife’s kitchen I changed the plumbing from two pipes to 3 pipes with a circulating pipe. water flows from the water heater to the kitchen back to just under the bathrooms and then back to the water heater. Then I also set the pump up with remote start. YOu want hot water push a button in the bathrooms or the kitchen wait about 1 minute and almost instant hot water. I am look at moving and if I can I will add the third pipe to the water system.

Talk about finding a complicated answer to a simple problem.

Why not put an electric water heater directly in the shower. One like this

I’ll do you one better. You can put the heating element right in the shower head itself.

That seems like a lot of extra work and extra plumbing that accomplishes the same thing as regular recirculating pump that you install in the bathroom and pump water out of the [not yet] hot water pipes and into the cold water pipes. It primes the hot water and as soon as you you turn the shower on it’ll purge all the luke warm water in the cold side.

Adding the 3 pipe was little trouble. The problem with the under sink hot to cold circ pump is pumping hot water back the cold water line can be a problem for other bathrooms or kitchen on the same cold water line. And again you will have to wait until the hot water is purged out of the cold water line before using the shower.

It depends:

The fastest way to get water to your bathroom ‘might’ not be a direct run but a branched run. This way any demand for hot water would pre-load the pipe with hot water, which would bring it closer to your shower faucet.

So if the water heater is far away from all hot water using appliances, it would be better to use a single pipe to move all hot water to a distribution point or use a branching ‘tree’ then run individual lines to everything.

If the branching tree method is already direct to your faucet (practically as direct as a direct run), there is no advantage in this sense of a dedicated run - except being able to isolate that run with a valve incase of pipe work so as not having to shut down the entire house of water, and possibly greater pressure.

I’ve had one of these for 17 years. Mine is a Metlund unit, and it’s great. walk into the bathroom in the morning and press the button. About 1 minute later, hot water at the sink and shower. And no water wasted down the drain. I’m in a rural area and water is somewhat expensive so that’s nice too.

In a large house with long pipe runs I had a sorta similar arrangement as @Joey_P. But IMO better.

There was one pump installed right at the output side of the hot water heater. It had a programmable timer that can be set to whatever hours of the day you want. At each room where you want quick hot water you install a bypass under a sink that connects the slightly pressurized hot side to the cold side through a one-way valve that has a mechanical thermostat built in.

When the hot-side gets too cool, the valve opens and lets pressurized hot water flow into the cold line. When the incoming hot water is hot enough the valve closes. Lather rinse repeat.

Most of our long pipe runs were inside the unfinished part of the basement, so it was easy to wrap the hot pipes in foam insulation. We never noticed a difference in energy consumption with the system running or not. It can’t have been zero cost, but it definitely wasn’t a big deal either.

The end result is instant warm-soon-to-be-hot water at that location with no need to pre-start a pump. You only needed one bypass valve in a bathroom even with multiple sinks, shower, and separate tub, since all of those are fed off the one long branch line from the HWH.

Because of my job we kept/keep unpredictable hours, so our pump’s timer was set to run from 3am to 11pm. Folks with more rigid schedules might choose to only run it from 6am to 8am and again from 5pm to 7pm.

A 3-pipe system with a circulator wastes a ton of energy even if you insulate the hot water pipes. So to mitigate that you need to use a timer or switch to turn it on. At that point you might just as well use the hot-to-cold water line pump like @Joey_P describes. Perhaps a motion sensor in the bathroom would work better so you don’t need to remember to flip a switch. I like the idea of having a small point-of-use heater that’s hooked up to the hot water line, so it will shut off once the hot water from the main tank reaches the bathroom. It doesn’t need to be huge in capacity because it never has to heat anything colder than room-temperature water. You’d still likely need 240v power to it though, and for something like a short hand washing you’re using double the energy (or more) because hot water is still pulled out of the main tank even if it never reaches the faucet. Maybe such short/small use is inconsequential.

The idea behind some plumbing systems is to have individual runs to each fixture from a central manifold. That way you can use the smallest possible pipe, like 1/4" or 3/8" for a sink instead of the usual 1/2". That way there’s less volume of cold water to flush out of the lines, especially compared to a typical branched setup which would have even larger diameter pipes closer to the water heater serving other areas of the house. In practice, long runs are still frustratingly slow, especially with very low-flow faucets. Also you can’t pre-flush the line to the sink by taking a shower, or vice versa, which can be handy if you’re going to shave at the sink after showering, or if you need to scrub your hands before showering. In total it’s still better than a traditional layout but it’s nothing like having a recirculator.

If you ever wondered why you get instant hot water from taps in a hotel, this is the system they use. Rooms are divided into zones and each zone has a hot water supply being circulated by a pump through heavily insulated pipes.

Blockquote
n large hotels, rooms are assigned risers, or pipes that provide them with hot water. Up to two gallons a minute travels through the riser.

“By keeping the water continually moving through each riser, we never let the water cool and get cold,” he says.

Baths or showers are only a few feet away from hot water.

Raed Shuwayhat, director of engineering at Fairmont Austin in Texas, says hot water is considered to be 120 degrees Fahrenheit. That is maintained through pressure- and temperature-regulated variable-speed pumps for both hot and cold water systems. The hotel has 1,048 guestrooms on almost 30 floors.

“When hot water demand increases, the system is designed for the main water pumps in the mechanical room in the basement to rev up speed and push additional hot water from the hot water holding tanks, and the pumps would rev down when the hot water demand and usage decreases,” he says.

Logical would be to hook the circulation pump activation to the bathroom vent fan switch or light. Perhaps during the daytime you have to make do with a delay, but at night or in the morning, you would be turning the pump on a few minutes before using the shower or tub, and the pump would stop when the bathroom fan or light is turned off. I assume a timer is plan B. Or perhaps the act of turning on triggers a timer - let’s say 10 minutes. If you haven’t used the hot water within 10 minutes of entering the bathroom - then it doesn’t matter?

I presume the way it works is the return hot water is attached with a “tee” into the hot water tank input feed, with a one-way valve to stop hot water from going back into the water supply feed instead? And a thermostat, so the pump only works when the temperature return is below a certain level?