RODI problems

I've had a bulk reef supply RODI unit that doesn't get 0 TDS anymore. According to the video BRS put out the RODI filters should last about 5000 gallons. Around a year. I only use about 40 to 50 gallons a month since my tank isn't that big. Sometimes I check the water and it will be 90 TDS and two gallons later it may be 6 TDS. It's done that from day one. Think maybe I got some bad filters from the start ? I can order the new filter and resin kit for $22 but I shouldn't need that after about 500 gallons. Any ideas ?

 

No one can say how long your DI will last, its impossible since everyones water conditions are different.

There are so many variables like water pressure, water temperature, TDS, hardness, CO2 level, waste ratio, how much water you make at a time, how well you store the system when it is not in use etc. Every one of these has an effect on how well a RO membrane functions and on DI life.

There is no way DI lasts 5000 gallons for the average user, far from it. Consider the average TDS across the US is 250 and say your membrane is a very good 98% rejection rate and you have no detectable CO2 in your water. Your RO TDS would be 5 going into your 20 oz vertical DI filter and we can pretty much assume a full pound or 16 oz of DI resin can attract 3,000 to 6,000 TDS so add 25% since you have 20 oz of resin so 3,750 to 7,500 TDS capability. 3,750/5=750 and 7,500/5=1,500. So under average water conditions with a 98% rejection rate off the shelf membrane which is not usually the case you can get 750 to 1,500 gallons maximum, real world numbers are usually on the lower side.

What is your water pressure, water temperature, tap water TDS, RO only TDS and RO/DI TDS numbers? What is your exact measured waste ratio?

You should replace the sediment and carbon block filters every 6 months and disinfect the system at least annually. The DI gets changed when you no longer see 0 TDS on a consistent basis but you want to make sure your RO membrane is functioning properly before replacing the resin or you could just be throwing money away on resin propping up a poor membrane.

 

From the day I got it brand new the TDS has varied. It was always low but sometimes it would be 5 or so and I could run another cup full and it would be 0. It has always jumped around. The membrane is supposed to last three years but who knows. I need to get one of those in like TDS meters.

 

You need good handheld TDS meter, not an inline which is not temperature compensated and not as accurate, plus they are dedicated to only two places and cannot be used portable.

To troubleshoot a RODI you need three TDS readings, tap water, RO only and final RO/DI. The inline only tells you two, usually RO only and RO/DI but you need to know the tap TDS to calculate the RO rejection rate which is 90-98% of the treatment process.

 

I have a portable TDS meter.

 

I could see your RO membrane lasting that long(5000) but not the other filters.

If you haven't changed any of the filters in a year I you need to change them all.

Pre-filters(carbon, sediment) should be changed every 3-4months. Once the Chlorine / Chloramine gets past the carbon and hits the RO membrane it's done for.

RO membranes people argue over 1yr to whenever the rejection rate drops to low.

DI is based on how high the TDS is coming out of the membrane. Which is directly related to the TDS coming in. Because the RO membrane is a % reduction.


Are you on Well or City water?

 

So, what are the three readings?

AZDesertRat is the water filter expert. He need those to help troubleshoot your filter.

 

What are you collecting the water in to test the TDS? You could be contaminating your sample. You need to thoroughly clean the cup or whatever with very hot water first, or you could be getting a false reading from TDS already in the cup.

 

I don't have the in line meter yet. I can test before it goes in the unit and after. I read up a little and I think I need the flush kit. I have just been sticking the hose in a bucket and turning the water on. Last night I let the water run down the sink for about ten minutes and then stuck the hose in the bucket. The TDS was 002. Going to go ahead and order the flush kit, in line TDS meter and all new filters tomorrow.

 

I didn't know that. I'll start doing that from now on. Thanks.