LONG Distance to shower. Best option?

[D C]

New construction. All electric. No gas. No propane. 400 Amp service to the house.
Wide ranch with the master bath on one end of the house, 2 additional beds/baths on the other end of the house, upstairs over the garage.
Primary water heater is in the basement, very close to the master bath, where the utility room/well-inlet are located.

The run to the upper bathrooms is on the order of 75-100' so we're looking at gallons of water in that supply line that need to be flushed in order to get hot water in the shower.

Kids are 16 & 22, so eventually these baths will see less usage as the older one moves out and the younger one is off to college.

We do need to be able to run both showers at the same time.

What is the most sensible option?
1) Recirculation pump?
2) Tank-heater upstairs? I have room for a lowboy water heater upstairs (and Lowes has a 38 gal Whirlpool-branded 6 yr unit on clearance right now)
3) Tankless electric upstairs?
4) Tell the kids to suck it up and wait for the water to run.

Thanks!
Dave

 

[Stuff]

In Michigan an electric tankless will probably disappoint with the cold water temperatures.

Have you talked with the plumber? Is the feed to the baths going to be individual PEX runs or a single feeder?

 

[Sponsor]

 

[D C]

My wife sleeps with the plumber, actually. (yes,I'm the plumber)

Running 1" pex across the main floor, both hot and cold. To continue upstairs, I'll either run 3/4 pex if it's both hot and cold runs, or a single 1" if I go with a separate water heater for up there.

 

[Smooky]

I would do it with a separate tank heater.

 

[Stuff]

The tank option seems to be winning. You could run an extra line to later use for a hot water line or circulator return.

 

[Jadnashua]

If your lines are or can be insulated, at least one study says it's cheaper to run a recycling system than to waste the water, pay the sewerage fees, and functionally, deplete the WH capacity. Numerous ways to set one up. If your lifestyle allows, a timer can lower the costs, or, if you're willing to be a bit more hands on, you can put a trigger at the point of use, but then have to wait for it to pump the hot around, but it may only need to run for a few minutes. Mine only runs maybe 5-minutes an hour or so.

 

[Dana]

A recirculation system makes the most sense, especially if it's controls are smart enough to only run the pump when water is being called (by a flow sensor, or a manual button.)

Even if you have big enough electric service to cover the extreme loads of the tankless required to cover a full flow shower at your incoming water temperatures, those very high short term loads abuse the distribution grid, which is infrastructure we all pay for. Some utilities are starting to implement "demand charges" in residential rates, to recover the costs of the infrastructure required to support very high peak loads. They are typically based highest use over any 15 or 30 minute interval during a billing period, and a $ times peak-watts adder is applied. A 10 minute 35,000 watt shower can be pretty expensive if your average draw over the month is otherwise 1000 watts, with 7500 watt peak under other conditions. This may be coming soon to a utility near you (or not).

With 3-4 showers/day for the upstairs baths there may be an economic rationale for a drainwater heat recovery heat exchanger, which will extend the apparent capacity of the water heater, and cut the electricity energy used for showering roughly in half:

 

[D C]

A recirculation system makes the most sense, especially if it's controls are smart enough to only run the pump when water is being called (by a flow sensor, or a manual button.)

Even if you have big enough electric service to cover the extreme loads of the tankless required to cover a full flow shower at your incoming water temperatures, those very high short term loads abuse the distribution grid, which is infrastructure we all pay for. Some utilities are starting to implement "demand charges" in residential rates, to recover the costs of the infrastructure required to support very high peak loads. They are typically based highest use over any 15 or 30 minute interval during a billing period, and a $ times peak-watts adder is applied. A 10 minute 35,000 watt shower can be pretty expensive if your average draw over the month is otherwise 1000 watts, with 7500 watt peak under other conditions. This may be coming soon to a utility near you (or not).

With 3-4 showers/day for the upstairs baths there may be an economic rationale for a drainwater heat recovery heat exchanger, which will extend the apparent capacity of the water heater, and cut the electricity energy used for showering roughly in half:

What purpose would be served by a recirc pump that only runs when there is a current demand for hot water? That's when you DON'T need the pump,right? It would have to be timed to preceed the need for hot water in order to be effective.

The more I think about it, the more a recirc pump is impractical. Great if you're on the same schedule every day. But what about that evening shower that happens periodically? Or the weekend the kids sleep late? Anything that's off-schedule throws the recirc pump strategy for a loop.

 

[Master Plumber Mark]

just install a water heater and install a Grundfus recirulation pump with a timer on it .......
have it set up to come on at 6 in the morning and shut off at 8am
then have it come back on at 5 in the evening and go off at 9...

this is extremely simple to do
and only on a rare occasion will anyone complain if they miss out on instant hot water
and who cares anyway??? Tell them to suck it up and stop being crybabies....
on an off hour , they will just have to wait a grand total of 30 seconds for hot water ...
So are they gonna divorce you
over this???

also those copper heat exchangers that go on a pvc drain line are a joke...

 

[Jadnashua]

Mine, similar to Mark's, comes on in the morning, and off about when I typically go to bed. Some people just leave them running 24/7. If your lines are insulated well, it doesn't add much to your costs. The pumps tend to be quite small, often in the order of 1/25Hp...it doesn't need to be huge.

If you put an occupancy switch in the rooms where you need hot water, the pump would turn on when you enter, and likely, have hot water once you get to needing it. Or, you could add a switch...you just need to turn it on and let it run long enough to get hot water there before you open the tap. Most people don't want to wait, so a timer (maybe with an override if you're needing hot water off cycle) tends to work well.

Depending on the system you purchase, some turn the pump on/off to maintain a desired temp. Some leave the pump running and use a temperature controlled valve that closes once you have hot where you desire it. Either system can work well. Mine works by sensing the water at the far point, and shuts the pump off once it gets the set temp. It tends to run about 50-60 seconds, about every 10-15 minutes...hardly noticeable electrical load.

 

[Master Plumber Mark]

Mine, similar to Mark's, comes on in the morning, and off about when I typically go to bed. Some people just leave them running 24/7. If your lines are insulated well, it doesn't add much to your costs. The pumps tend to be quite small, often in the order of 1/25Hp...it doesn't need to be huge.

If you put an occupancy switch in the rooms where you need hot water, the pump would turn on when you enter, and likely, have hot water once you get to needing it. Or, you could add a switch...you just need to turn it on and let it run long enough to get hot water there before you open the tap. Most people don't want to wait, so a timer (maybe with an override if you're needing hot water off cycle) tends to work well.

Depending on the system you purchase, some turn the pump on/off to maintain a desired temp. Some leave the pump running and use a temperature controlled valve that closes once you have hot where you desire it. Either system can work well. Mine works by sensing the water at the far point, and shuts the pump off once it gets the set temp. It tends to run about 50-60 seconds, about every 10-15 minutes...hardly noticeable electrical load.

the simple way with a common timer is usually the best way to do something like this...
the added expence of occupancy switches complicates matters and seems like you are going overboard
in an attempt to make your system like a very expensive hotel or hospital.... I suppose it can be done
but the risk of 24/7 hot water flowing for years on end outweighs the benefit....

#1 leaving the pump running 24/7 absolutely kills off a water heater at a much faster rate.

#2 I have seen many systems installed in L copper pipe where the 24/7 hot recirc line
begins to get pin-holes in it due to the copper thinning out and the whole hot water line
from start to finish begins to wear thin too ....this is very bad and can amount to be big trouble

installing new copper water lines in a finished home is not an easy or cheap process
and catching a pin hole leak before it breaks loose to do major damage is also not done easily

I have not got a clue as to what kind of wear and tear PEX pipe can handle
with hot water constantly flowing through it.... but I dont think it can be good....

carry on....

 

[rjbphd]

Don't need re-circ pump on hot water return line if it's properly installed.

 

[Dana]

What purpose would be served by a recirc pump that only runs when there is a current demand for hot water? That's when you DON'T need the pump,right? It would have to be timed to preceed the need for hot water in order to be effective.

The more I think about it, the more a recirc pump is impractical. Great if you're on the same schedule every day. But what about that evening shower that happens periodically? Or the weekend the kids sleep late? Anything that's off-schedule throws the recirc pump strategy for a loop.

Quite the contrary, it only needs to be pumped when you DO want the hot water to arrive quickly, after a period when it has cooled to some tepid level. At a pumping rate of 5 gpm the fully heated water can arrive through 100' of half inch plumbing in under 10 seconds, whereas at a 1 gpm washbasin tap flow it will seem like forever.

Timers are a solution if your use schedule is really regular, but it wastes energy to run it when hot water may not be called for another 15 minutes or more.

 

[Jadnashua]

As I said, some run the pump continuously (while enabled), and some (like mine) turn the pump on/off with some hysteresis that keeps the water at least warm (mine's adjustable) at the sensing point. In reality, my pump only runs about a minute a few times an hour. The rest of the time, everything is essentially off except for the sensing circuit. There are lots of systems out there, mine happens to be a RedyTemp, which was quite easy to install, almost without needing any tools. I had power where I wanted it, so it took all of about 10-minutes. You do pay for that convenience, but it's been working for about 12-years now without issues. I've gone through 2 timers, and I think it's time for a new one, but that is not part of the unit itself. I've had both digital and clock motor timers fail over time, but they're cheap.

 

[Flat_Twin]

Option 4. Simplest and least expensive choice. First one to shower in the am at our house knows to run the hot faucet at the sink for 15 seconds.

 

[Jadnashua]

FWIW, in my townhome, it takes over a minute to get hot water into the shower if I get up before the timer kicks in on my recirculation system. The time it takes depends on how far and how big the pipes are, and, whether you have heat traps on the WH ports...you have to flush out the room-temp water, and then, there's a little loss in warming up the pipe along the way. Depending on how the pipes are run, in the winter, warming up the pipes can be a considerable impact and lengthen the time it takes for full hot water at your point of use. You can end up wasting a bunch of gallons of water if it must happen many times during the day without recirculation. And, keep in mind that those gallons that go to filling up the pipe with heated water are being replaced in the WH with cold water, thus decreasing the amount available for your instant use.