i have a new 3 stage ro unit,
now in the past i usually get about 16ppm readings with my old filters
now it seems I'm getting 28-30ppm my tap water tds is 310ppm
any reason for this could the membrane provided be the problem?
With a new unit you need to flush about 20-30 liters through to remove the carbon dust and other various contaminants from the manufacturing process. You know it's done flushing when you get a reading similar to the old one.
i flushed the unit for over 2 hours yesterday night and now again for about a hour, they are going down by a few number but nothing much
also when i first switch on the unit i get tds readings of about 80ppm after a few minutes the drop back to the 30 range
Am I correct to think this is a new unit and not replacement canisters?
You should be able to get 0.0 TDS really, as @lilirose says they sometimes take a bit of flushing but that's quite a lot.
Get a pump on it, I found it so much better using one that had auto flush etc and worth it's extra expense easily.
I hope they start pushing through 0.0 soon, you could always add a DI cartridge on if it's not already on there but is even more resistance, I know.
yh it a whole new system, left it on for like 4 hours now, tds is at 26ppm, its usually half that number
.you guy think maybe the membranes shot?
its one of those cheap 3 stage units from eBay.
this time the ratio of waste water to Ro water is 50/50
usually its like 70/30 waste to ro with my old filter.
any reason for this change in this quite significant waste to RO production.
I no longer use RO/DI but brought a Vertex unit when they first brought them out a few years back and that pumped, flushed etc automatically and I never really had much of a run in time on filters. Quality units and canisters are worth the investment in my opinion, quicker production, less waste, auto flush etc. No idea what's on the market now and I was fortunate that the retailer put the wrong price up so was £100 cheaper than it should have been.
Have you ever wondered if it's your TDS meter? You should be able to get a 0 reading and even the 16PPM from your old unit is well above what you should expect.
Just my opinion, maybe a question you will get better response and experience from a reef forum.
Depending on the brand, RO membrane quality, pressure etc the TDS of the water is going to differ a fair bit.
As a general rule, an RO unit working at maximum performance will have an efficiency of about 98%, most important is the water pressure of about 60-80 psi but different units have different requirements. Then there is prefilters, water temperature etc which all affect performance.
I would keep it flushing for a few hours and if needed add a DI unit.
As a comparison, my tap water ranges from 40 to 70 odd TDS and even my RO unit would not bring this down to 0 without a DI unit. I usually get 1-2 TDS after the membrane.