I have a whole house tankless water heater installed, and so far it's nice except one problem. I also have a nonelectric hot and cold toilet mounted bidet installed. Since a high pressure jet would not make the bidet suitable for it's task, it's max output is less than 0.4 GPM.
The tankless heater has an activation flow rate of 0.4 GPM and the bidet fails to pull enough water to start it heating.
The current solution is to run either the sink or tub hot water to avoid a very cold jet of water in an uncomfortable place.
Is there a common solution to this issue?
I'm considering getting a 2 gallon mini tanked water heater for the bidet. I think that should be plenty, but I'm worried that a small tank heater would have a lot of surface area and lose heat fast. It would have the advantage of being local and instant, as long as it was installed near the toilet.
Alternatively I could get point of use tankless water heaters. I have one installed in the kitchen in series with the whole house unit to boost the temperature for the faucet and dishwasher. That works good, but I'm having trouble finding one with a low enough activation flow rate for a bidet.
A third option is to use an electric bidet. This has some nice bonuses, but I don't really want to do that. They're expensive, and since they're all in one units, then each additional function is an additional point of failure. I'd rather keep the bidet and water heating separate. Further I already have the bidet, and toilet seat, and don't want to replace them if it's reasonable and possible.
So what I'm looking for is more information.
How is a low flow appliance normally handled with a tankless heater? Is the minitank a good solution energy wise? Should I look harder for low flow point of use tankless heaters? Is there something I'm not aware to solve this? Thank you.