Wondering Where I Went Wrong

[Keitha333]

I am wondering what I did wrong as my membrane started to pass about 1% sugar. I use a single 400 gpd RO filter (After 5 micron pre) I like playing around and was testing sap and concentrate percentages and for kicks I tested the permeate as well. it read 1% to my suprise. I immediately thought I needed to recalibrate but got distracted. After boiling down I realize it was reading correct. I got 48:1 way off my 10 year average of 35:1. Last year was my first year with an RO and at the end of the season I did a lengthy permeate rinse, stored it in permeate in the fridge. This year I did a rinse, soap wash of ph10, rinse and used. I am wondering if the water I rinsed with still had Chlorine in it even after sitting out for 3 days.... Would that possibly cause my issue? Nonetheless a new membrane is on the way!:cry: Thoughts?

[ecp]

10ph sounds low to me for a soap wash. Have you tried an acid wash? That would help close the membranes up.

[Keitha333]

I have not....the 10ph is what the membrane was rated for which is why I didn't go higher. So your saying that an acid wash would possibly help? I can try that. Does that shrink the microscopic holes a little in the filter?

[DrTimPerkins]

An acid wash will help tighten the pores in the membrane and will remove any mineral build-up. Sometimes it is enough...sometimes it is not.

[ecp]

In general (10 thousand foot view) a soap wash (High PH level) opens the poor's in the membrane so you can push the crap through them and out. Conversely and acid was (Low PH) shrinks the poor's to loose the crap on the membranes. If you are doing an acid was it is a good idea to first do a soap wash, then rise, then acid wash, then rise then soap wash, then rinse. Basically (again 10 thousand foot view) push the stuff through that will go then loosen the rest of the stuff and finally push that through. Like Dr. Tim states this is no guarantee, but soap and acid are a lot cheaper than a new membrane. Hope this helps a bit

[DrTimPerkins]

Yes, doing an acid wash is usually part of process in which you:

purge sugar (if you've been concentrating sap, otherwise you can skip this step)
rinse
soap wash
rinse
acid wash
rinse
soap wash
rinse

RO soap is a strong alkali (essentially lye) that will burn off organic materials and open up the membrane and acid will dissolve any mineral substances and tighten the membrane.