RO/DI Automation and TDS creep


Premium Member
Maybe get some life into this forum ;)

Almost 2 decade ago I began building an automation system for my reef. This was in the infancy DIY accessible microcontrollers and components. I built a rather complex RO/DI system as part of that project, complete with custom designed PCB, a rotary encoder, and all kinds of telemetry. It calculated reject ratio, total waste, accumulated product, filter life, etc. It was a fun project, but overkill for the purpose at hand (somewhat clean reef water).

I never actually fully finished the reef controller or remote software and (as many of you know) basically let my tank freewheel for the better part of the last 10 years. Sometime 5 or 6 years ago I took the RO/DI system offline and have no clue where the electronics package went. The same holds true for the reef controller. (She throws things away sometimes when they have collected dust for too long... )

I purchased a Profilux 4 - so will not be temped to or have a need to expand this project into a never ending scope.

The goal is very simple.

I will setup a small Microcontroller to time a sequence of relays anytime there is a call to fill the RO/DI resevoir.

1 - open fast flush and clean membrane and send water to waste.
2 - bypass DI resin and send water to waste.
3 - send initial output from DI resin to waste.
4 - send product water to reservoir.

Simple code and a few solenoid valves. The timing for each step will be hard coded, No need for a human interface.

I will try to post progress here. Parts should arrive in a few days (yes, even most of the electronic parts boxes are gone).

If I get bored, i will add flow transducers and TDS metering to the project with an LCD, but they are really not needed.
Wow kinda spendy for a solenoid and some basic logic, but assume it is a quality product being from SP.

I think one could package a small black box retrofit with 2 solenoids and a timer relay for far less... Then again there is supporting what you sell, which is very costly and what most "I can make money in this hobby inventing hardware" people miss.
I have most of the hardware sorted out and the basic interface and code worked out. I will update here in a few day to show some of the progress.
I did not go into it in detail but @ MACNA in Milwaukee Spectrapure made the RO water.
Charles told me he was getting more product than waste with the new system.
Oh I am sure you could get the waste down to less than 1:1 by cranking down the flow restrictor. The question just becomes membrane life at that point, even with flushing I assume the membrane costs far surpass the savings in water. I hate to see that water go down the drain and hate to pay for it. Setting up a system to capture and pump to plants during warm months also costs more than the water it saves. I keep considering it though...
Not sure how far you got with this, but I use my Hydros to control my RODI with auto flush. It flushes the first minute and again every hour it is on for a minute. That is built into RODI output type. That is ok if you are just refilling to one container butI refill to my DI container and my mix tank. Below is screenshots of the main RODI output settings. It will control the feed output device which I use to turn on a solenoid on the input of the RODI.a flush output device. I can control a flush output device which I have is a solenoid I paralleled the manual valve in the RODI with. It can also control a boost pump which I do not have on the RODI. Normally you would also use water level sensor for the high level and low level inputs but since I am going to use another output to turn this one on I created an input on one of the sense ports that is connected to relay contacts. The relay is powered by the output I use to control the RODI. This way I get to use the flush on the mix tank refill, DI container refill and the timed refill of the RO bladder for the ice maker for the fridge. That is all accomplished by other outputs. To begin with before they came out with the RODI output type I did it differently and did not have the flush valve. I have a build thread hereon Reef Central that has all the screenshots of all outputs and related inputs. It is in several places which I will post below. Here is a link to the build thread at page 5 where the first of the RODI setup is posted Hex Tank Build .

RODI setup original setting post# 98 on page 5
RODI using RODI output type minus flush valve post# 111 on page 6 (This only goes over the differences from first post)
RODI using flush valve post #150 on page 8 (This also only goes over the differences from the other posts)

I was going to do this like you but once I got the first Hydros controller I decided to use it to do this. I originally got it just for the garage mixing station and RODI but eventually expanded it to the the tank also.