tub capacity & Rinnai hot water heaters

We were initially looking at the size of a large standard tub and note its dimensions of 1.8m x 1m x .616m. However, these measurements seem to be the exterior dimensions and thus we can’t really tell the interior volume of the tub, and how many liters/gallons it would take to fill the tub.
We are are also unsure of the volume of the tub for this one as well. 471mm may be a bit too shallow for us but we also don’t want to have it too high given the amount of water it takes to fill the tub. Given volume of hot water issues, do you also work with clients that use a hot water pump/ heater to save water and heating costs?

Please note that we can do any size (of course it has to fit in a container…) so you do not need to be bound by the photos on the HP.

To calculate the capacity in liters you can use the formula: L-70mm x W-70mm x internal depth.

For instance, the 1.8m x 1m x .616m will be about 1m3 = 1000 liters = 264 gallons

For the water heater, you should check with your plumber. I am aware that a Japanese maker (Rinnai) is increasing its presence in the US market.


They offer gas-powered instant/unlimited output hot water heaters (so no problem with the capacity) with a built-in water recirculation function.
I recommend contacting them directly for more information.