RO/DI Membrame...???

[charles6299]

how do i know when i need to change my membrame ? i filled up my 125 gal. tank yesterday and everything was running fine....i have an ASOV .......today, its barely making any water..like dripping, and making 10 times more waste water.......what could be the cause of this ? the membrame is only 2 months old.....

 

[AZDesertRat]

The way to tell if it needs replacing is by TDS readings. If you have a 75 GPD Dow Filmtec membrane it should be giving you 98% rejection or removal. In 3 years or so it will slowly drop to more like 90 to 95% where you should change it out. If it is a 100 GPD membrane it should start out closer to 90% rejection rate and if it were me I would replace it when it gets about 88% but I would replace it with the more efficient 75GPD Dow at that time.
As for you problem, what is your water temperature and pressure? Those could be your problem. Another could be, if you have a flush valve it may be in the wrong position and not allowing full pressure to enter the membrane.

 

[charles6299]

no flush valve.......why would i be getting good flow yesterday, and today just dripping ? is it working better now ?

 

[AZDesertRat]

Are you saying you made 125 gallons of water in one day? That is not normal if thats the case. You can usually figure 2/3 to 3/4 of the rated capacity is what most people get per day so a 75 GPD should make 50 to 60 GPD and a 100 would make 65 to 75 or so. If you made more than that in one day I would suspect your water was not being fully filtered.
Use a measuring cup and time the output to see how many GPD you are getting. And yes output can change from day to day if pressure and/or temperature changes.

 

[charles6299]

THATS WHAT I AM SAYING....WHY WOULD SO MUCH WATER BECOMING OUT FOR A COUPLE OF MONTHS THEN ALL OF A SUDDEN....ITS SLOW..........IS THE MEMBRAME STILL GOOD ?

 

[AZDesertRat]

Do you have a TDS meter, if so check the TDS of your raw water, RO water and RO/DI if you have DI. Also it helps to know your water pressure and temperature, both have a great influence on output. Usually if membrane produces more than its rated flow it is either due to not being seated properly in the housing and water is bypassing and not being completely treated. TDS will be higher than it should be in this case.
Also if your water temperature and/or pressure are higher than normal you can get more flow. This is a good thing in these cases.
I would suggest doing a timed measurement of flow with a measuring cup and clock to see what the GPD figures out to be along with the TDS measurement I already mentioned.