Ro/Di Initial Startup Water Flush

This is the change that I have made, illustrated in the 2nd and 3rd picture. Hopefully what I have done makes sense now. Its purpose is only to prevent anything other then 0 tds water from going into the barrel.

 

Again, the amount of TDS creep is minimal and is easily diluted in your storage container.
I have a 23 gallon Rubbermaid recycling can for my ATO container. It has float switches installed 12" apart so the level muct drop 12" or a calculated 11 gallons before the RO/DI comes on again. The container has been in use over two years, has never ever been drained or cleaned in any way and the TDS in the container is still less than 1 TDS using a HM Digital COM-100 handheld meter. My tap water TDS is 560, my RO only TDS is between 2 and 3 and my DI is 0 TDS. The system is a MaxCap UHE ultra low waste and the DI lasts about a year per cartridge with my 100G mixed reef and 16G nano.

Everything is automated so I don't flush anything on start up but the UHE does flush the membrane with stored DI water then pickle it or immerse it in DI water when it is inactive so it always stays flushed and does not suffer from TDS creep.
This is my fifth RO/DI system over the years and they have gotten better each time but even with my first 90 GPD MaxCap TDS creep was not a huge issue and my tap water TDS was around 800 at that time, DI still lasted over 800 gallons per cartridge.

 

Isnt the U.S. drinking water standard <500 mg/l for tds? It may not be a huge issue just part of my nature. If I didnt use the valves I would be pulling the hose out of the shut off valve every time I ran it to do my initial bleed. I think this way will work much easier then that plus it gives me access to RO water for whatever purpose I may use it for.

 

There is no EPA MCL for TDS. Since TDS is considered and asthetic problem and not a health risk there is only a suggested guideline of 500. This number was pulled out of thin air and really means nothing since in the Southwest and many other locales it exceeds that number significantly. Here in AZ you don't even have to guess why they named to Salt River salt! Or have you ever wondered where all the rock, minerals and soil went from the Grand Canyon when the Colorad River carries it away? In the lower parts of the Phoenix metro area the TDS exceeds 1200-1600 and in the very best areas it's still over 500.

It is a non enforcable standard and not a Maximum Contaminant Level since TDS is not a measurement of anything specific and by itself does not pose a health risk. Sort of like hardness, it can be a nuisance but will it kill or sicken you?

 

Very interesting I did not know all that.

Thank you for the info to improve my design. I am glad that I changed the placement which should keep my anal nature happy and also hopefully provide a slight benefit to the DI resign.