# POU water heater experience



## uts (Jul 8, 2019)

Looking to add a few POU water heaters in the kitchen and bathroom. 2 of our bathrooms take a fairly long time to get water. You are almost done washing hands/face by the time the warm/hot water appears.

I read through a bit regarding both tank and tankless options and seems for small/undersink options the tankless is space conserving but both perform equally?

Would love to hear other peoples experience and any recommendations.

Thanks!


----------



## ionicatoms (Mar 8, 2020)

Watching


----------



## uts (Jul 8, 2019)

Just bumping this up to see if anyone has had any experience?


----------



## ionicatoms (Mar 8, 2020)

We're planning on getting a whole house unit. Natural gas heater. But the darn thing needs power or it won't kick on, so I would like to have a standby generator too.


----------



## jayhawk (Apr 18, 2017)

'whole house unit' not sure how it'd accelerate it ....still have miles of (oversized) pipe in front of a sink ...shower ?
So :thumbup: on electric POU


----------



## Boy_meets_lawn (Sep 27, 2020)

A recirculation loop is another option. Some of the newer thankless units have the option built in and you can either run a return line or they make a retrofit adapter.


----------



## Ware (Jan 28, 2017)

Boy_meets_lawn said:


> A recirculation loop is another option. Some of the newer thankless units have the option built in and you can either run a return line or they make a retrofit adapter.


We have a Rinnai with the built-in recirculation pump. Our house was plumbed with a loop, but you are correct that they have a thermal bypass valve that can be installed under a sink in a home that doesn't have a dedicated return.

You can trigger it with a motion sensor or a push button, but we just run ours on a schedule through the app - e.g. weekdays from 5:30am-8:00am and 5:00pm-10:00pm, and weekends from 6:00am-11:00pm. You can put it in vacation mode from the app if you know you're not going to be home, and you can "recirculate now" for anywhere between 5min and 5 hours if you're home and need hot water outside of your normal schedule.

When it is recirculating we get hot water from any fixture in the house within 1-2 seconds. I would say that's one of the biggest differences between a recirculating system and a POU water heater - with a POU water heater you will only get hot water where they are installed. Also keep in mind most of those electric POU tankless water heaters are going to require a 30A circuit and will only give you up to around 1 gpm of continuous hot water. That's enough for hand washing, but probably not showering.


----------



## Ware (Jan 28, 2017)

ionicatoms said:


> We're planning on getting a whole house unit. Natural gas heater. But the darn thing needs power or it won't kick on, so I would like to have a standby generator too.


I have seen these battery backup units designed specifically for holding up a tankless water heater, but for about the same price you could buy a little ~2,000W generator from Amazon or Harbor Freight that could keep your tankless powered up and keep your refrigerator cold during an extended outage. You would have to drag out some extension cords though.

We installed a standby generator at our new house. It stung a little, but by this time next year I will probably forget how much we paid for it.


----------



## ionicatoms (Mar 8, 2020)

Ware said:


> We installed a standby generator at our new house. It stung a little, but by this time next year I will probably forget how much we paid for it.


The guy I talked to about a standby generating unit said that because I've got the variable speed inverter compressor in my HVAC that he would only quote me a Kohler for the whole house solution. I'm not ready to kick off the project yet, but I know it's going to be $$$ if I ever do it.

I think we're going to hit the windows and doors as our next big project and just take our chances with the utility company.


----------



## wingless (Jan 28, 2019)

When I did a total / major remodel of my small 2 bed / 1 bath southern FL home I eliminated the 35 gallon water heater and replaced it with a 18kW tankless water heater mounted on an interior closet wall.

The 18kW Rinkmo heater I purchased appears to be well made and well designed. The usage of a tankless water heater requires proper selection, based on expected water consumption and based on inlet water temperature. The southern Florida application is best / easiest because the cold water never gets really cold.

The printed and web documentation has zero mention about external valves that may be required or appropriate for the installation. For my installation I incorporated a 3/4" tankless isolation valve kit w/ a 3/4" over pressure / over temperature valve, per the local requirements.

The copper plumbing for the 3/4" safety valve slopes downhill to the exterior of the structure, w/o any valves, w/o any reduction in size, w/o any trap, ending at the specified height above ground, all per the local code.

My two 8/2 NM-B wires are routed to the main exterior panel, run through 1" Schedule 40 electrical conduit, attached to the exterior wall on the side of the house, then into that exterior panel. The 1" conduit size is great for two of the 8/2 NM-B wires.

A pair of 240VAC / 40A THQP240 breakers is used to supply power to the wiring.

The valve kit I used permits periodic usage of a tankless water heater cleaning kit, to run vinegar through the tankless heater, to remove scale. There is zero mention of cleaning in the tankless manual or the web page.


----------

