Wash tank heater ideas?

[cjf12]

At Lowes tonight on trip # 4,283 for some more plumbing fittings and I saw electrical elements for hot water heaters.
I have a stainless pot with an extra 1" hole. Are these accurate with the temp control that comes with them? Any one have a good heater that can be adjusted to shut off at appropriate temp?
Even a drop in will work. Just would like something I can set temp at and walk away if possible.

[wiam]

In my experience water heater thermostats at not very accurate. My last RO had a water heater element in it that was controlled by a pid and a relay. Also put a float switch in the tank. So it would turn off element if the tank got low.

[maple flats]

I use one very much like this https://www.amazon.com/Happybuy-Propane-Tankless-Upgrade-Regulator/dp/B07SW4VTQ1/ref=sr_1_4_sspa?dchild=1&keywords=propane+tankless+water+heater&qid=1613918722&sr=8-4-spons&psc=1&spLa=ZW5jcnlwdGVkUXVhbGlmaWVyPUEzQjFONDE1S04yTFdPJ mVuY3J5cHRlZElkPUEwMTc0NTAwMjNMOEkzMkhPWEVKTSZlbmN yeXB0ZWRBZElkPUEwMDQ1OTIwMkg0WUtVN0JaNTBPRiZ3aWRnZ XROYW1lPXNwX2F0ZiZhY3Rpb249Y2xpY2tSZWRpcmVjdCZkb05 vdExvZ0NsaWNrPXRydWU=
Just drain the unit when you leave. I drain mine by just shutting off the inlet source (a line from my permeate tank), open a drain valve for the cold water, and open the hot water valve, it drains completely. It give me all of the water I need, at up to just over 3 gpm and at 110 F with 35F water in. Fires on propane.
When cleaning the RO, if I need to raise the temp faster than what the pump will do, I route the permeate, thru the heater and back to the wash tank.