This table says to give a shower 2.5 GPM. If I guesstimate that 10 kW ought to be enough, at 240 volts that is over 40 amps. 8 kW would still be over 30 amps. In conclusion, I’m no electrician but you will possibly want 40 or 50 amps available.
I’d ask/tell them, not suspect them.
At a minimum, document the exact stud & firebreak locations for the walls anywhere you might later want rails. A cloth tape measure tacked up across the studs and some phone pics before the walls get closed is quick and easy. Stud finders are great inventions, but work less well through tile, backerboard, etc. Knowing where the structure is or isn’t is darn handy before cutting / drilling into expensive to repair wall materials.
[I haven’t read all the replies]
After/along with which, galvanized tends to develop any number of (often pinhole) leaks.
Which have been the bane of my mother’s existence. Sometimes – as in her case – the pipes can be hydro jetted and then epoxy lined, restoring the internal diameter and flow while eliminating the leaks.
Replacing is safer, though, particularly if nothing destructive would need to be undertaken solely to repipe.
We have a recirculating hot water loop on a timer and enjoy having hot water almost instantly. It’s not quite hot right from the go, because the water in the pipe between the loop and the tap isn’t hot, but that’s what, 2-3 seconds of flow? The timer is set to circulate from about 7am to 10am, then again from 6pm to about 11pm. It came with the house and we’re very happy with it.
My mom’s house is a rancher that has two bathrooms at one end, and the kitchen, laundry, and a half bath at the other. The water heater is in the laundry room. The pipes have a long LONG run through a concrete slab, so it takes a long time for the water in the master and hall bath to get warm, and my dad set the water heater temperature so high in an attempt to compensate that the water coming out of the kitchen tap is probably dangerously (as in scalding temp) hot. (My mom is used to it and won’t let me turn down the water heater.) Dad thought about putting a small water heater in the hall bath cabinetry, perhaps just 10 gallons or so, plumbing it inline with the hot water line. His thought was that they’d have hot water pretty quickly to the master and hall bath from the small water heater, and by the time that tank was out of hot water, the draw from the main water heater at the other end of the house would be hot enough, but he never got around to it. I suggested a tankless heater instead of a small heater, but he was so disappointed in the tankless heater he experienced in NINETEEN SEVENTY-ONE that 40 years later, he refused to believe the tech had gotten better.
When my brother and his wife did their remodel, they went tankless, but the way their house is designed, there are short runs from the water heater to every outlet, so it didn’t matter. ISTR he loved the tankless, both for efficiency and for never running out of hot water (his step-daughter and his wife loved long, hot showers).
No answers, but food for thought. I guess before I could recommend anything in particular, I’d want to know more about the layout of the house.
(edited TWICE to correct typos)
I love my re-circ system and the nearly instant hot water. I have a gas powered water tank and will consider something else when it dies which I hope is many years from now. I have a raised foundation in a temperate area and the pipes are insulated with pool noodles. The pump has a timer function but I don’t bother with it.
One full bath in basement across from furnace/laundry room that houses current hot water heater, powder room directly above that bathroom. Upstairs full bath above that. Biggest demand is the upstairs shower.
If the three main users of hot water are mostly directly above/below one another (or a relatively short run), I’d go tankless and not worry about a circulating system. Maybe install the tankless heater adjacent to the powder room - if you’re lucky enough to have a closet next to the powder room, that’d be perfect - so the runs in the house are short, either directly up or down one floor. That’s similar to the layout of my brother’s house. The kitchen and laundry (where the tankless heater is installed) share a common wall, there’s a full bath eight feet across the hall from the laundry, and the master is directly above the laundry.