I've put in a couple brands of UV and NEVER seen one that had an internal flow control. They ALL recommend installing an external flow control to prevent overrunning the unit....they tell you a flow that the unit is effective at, so you won't overload it....
I found those that didn't have an internal flow control to be a bit less quality and usually the class B lights. In my other post I led people to believe that the strength is either 16 or 32,000 and I should have added most class As go to 40,000.
cilcil... I don't suggest draining a hot water tank, there wouldn't be enough chlorine in it to justify that.
To disinfect a water heater all you have to do is raise the temp to 140f for 30 minutes to an hour, and prevent anyone from being burned. That kills all types of bacteria.
Unless the glass lining of a water heater is broken, chlorine can not harm a water heater.
E-coli bacteria is a serious health risk and it can not be detected by smell, taste or seen. It can make people very ill in a short period of time.
Internal fllow controls are usually made by Dole and in the form of a washer called a button, with an engineered flow directional hole to meet the specific max gpm. They use the same buttons in their external flow controls.
All water softener and backwashed or regenerated control valves use the same type internal flow control buttons. They, Dole, usually are very accurate because they are flexible to meet various pressures and flows up to their max rated flow.
You probably could not disinfect/sanitize a used septic tank with bleach if you tired to. Even if you filled it with straight bleach, or hydrogen peroxide.
And if you could, using the toilets again adds enough bacteria to start it working again anyway. just like when it was new and never used.
RO should never be used on health related bacteria contaminated water or on water that has harmless bacteria in it such as iron. manganese or sulfate reducing bacteria.