New RO/DI unit

[Waters]

I am using a Bulk Reef Supply 75gpd day RO/DI unit for the first time. After flushing the system for the first time (for an hour), my tap water is reading 001 TDS and my "good" water is reading 000. Is it possible that my tap water is that clean or is something wrong with the TDS meter? Everything came preinstalled.

 

[Waters]

Ok, I may have answered my own question (reading the instructions helps). It states that the "In" reading monitors RO performance while the "Out" reading monitors DI resin performance. So does that mean that it is not reading the quality of the water anywhere directly from the tap?

 

[Reefer_lou]

For that you would have to buy a single TDS meter from them only about 25 dollars I think and install it in the red line right before it enters the first stage

 

[Reefer_lou]

A single inline Tds meter not the handheld one. I have the same system and you just need to buy one that has one Line instead of 2

 

[AZDesertRat]

That is one of the disadvantages of the dual inline TDS meters, they are dedicated to two spots and you need to be monitoring three. I would highly recommend buying a good handheld TDS meter, it is much more accurate and can be used portable to test from any point such as tap water, RO only, RO/DI, bottled water, your ATO storage, the LFS water etc. Forget the inlines all together since they are not temperature compensated and lack the accuracy you want for RO and RO/DI water. The HM Digital TDS-3, TDS-4TM and AP-1 are all good choices for $25 or less.

 

[Palting]

I have 3 TDS meters, but the tap water one is not needed. Tap water from a community source has a pretty constant TDS. So long as the TDS after the membrane is 1-3 and the TDS after the DI is 0, there is no need for a tap water TDS meter. My tap water TDS meter always reads 170-190, wasted some money to get that TDS meter. The only time I would consider checking your tap water TDS is if you suspect your membrane is faulty ad you want to make sure you are achieving a 95%-99% clearance rate. If so, you just need to temporarily connect one of the TDS sensors to the tap water line to get a one time reading.

 

[AZDesertRat]

No that is not always the case. Tap water changes, it can be daily or even hourly, I should know since I was a municipal water system operator and manager for over 25 years and a well driller and pumping systems contractor before that. Today I help design, build and then teach operators how to run plants with a major engineering firm. The tap water TDS is very important since it is one of the two numbers used to calculate the RO rejection rate and the RO membrane does 90-98% of te work, the DI is just a final polishing. You cannot put a number like 1-3, it all depends on the sorce water and how well the membrane is working, the RO TDS should be around 96-98% lower than the incoming water, whatever that is. Again you need 3 TDS numbers, tap, RO only and RO/DI and all are very important just as knowing your exact waste ratio, water pressure and water temperature are since all have a direct bearing on how well the system works. Many vendors will have you believe RO/DI is plug and play and forget it but if you want an efficient system with long component life it requires a little work on your part like the TDS and waste measurements.