The membranes have different efficiency rates.

Filmtec 50 gpd = 98% rejection rate
Filmtec 75 gpd = 98%
Filmtec 100 gpd = 90%
BFS 150 gpd = 98%

If your tap water is 225 ppm, and you're getting 18 ppm out of the RO, then your efficiency is about 92%. If I were you, I would change out your flow restrictor for a 75 gpd, and get a 75 gph membrane that is 98% efficient. This way you should get about 4-5 ppm out of the RO, and your DI resin will last much, much longer. This is probably your cheapest solution.

I'm running single digit TDS, not zero, but don't think it's the end of the world (this is considering the cups of salt mix I add, the Dow Flake, the Mag Flake and some people do keep reefs with tapwater).

I'm getting the readings after the RO and DI.

My source is 500-700PPM, and I routinely get 10-11PPM after DI

Flow restrictor? What exactly is that? Is it the valve on the input or the metal valve on the output? Or is it something else? Are you saying I will need a whole new RO membrane?

Also, how do I flush the membrane? Do I turn the wastewater so none comes out of it or do I turn it so it's as high as it can go?

This is really disappointing...I can't afford to buy a new membrane, nor a booster thing.... I do have some DI here...should I just suck it up and change the DI a gazillion times? :sad:

How high can TDS safely go before I have to change things? 10? And if I have TDS should I be using Prime in my water?

Aqua-safe instructions, section 7.1 talks about the flushing valve and the handle position.

Myka is absolutely correct. Your unit is working correctly but because of the lower rejection rate of the membrane you are using up DI resin very quickly. This is why the Aquasafe units are cheaper but also not very effective with Alberta water.

The flow restrictor on the Aquasafe isn't a capillary type like used in most systems, it's built into the flush valve so if you do decide to get a new membrane you will also have to replace the restrictor, it costs only a couple dollars.

You will have to decide when you want to swap your DI, it's not a clear cut choice. 6ppm probably isn't a big deal but it depends what that 6ppm is. Test the water for phosphate at least and if you start to see that come through then it's time to replace the DI. Spring is here so you can expect to see some more phosphate then usual.

I think you will defineatly have to buy a booster pump, those aquasafe units seem to be real fussy about pressure. DO NOT buy one from one of these outfits in red deer. check out www.purelyh20.com the booster pump will run you about $100 (as opposed to $300 here in red deer), a new membrane in the 75 gpd flavour will cost you about $30-$40 with the flow restrictor and flush kit (highly recommended). Make sure you insist on USPS for shipping otherwise UPS will whap you with a big brokerage fee. If you need DI, littlesilvermax is the guy to grab it from!!

Also, if your turning the source water on and off all the time, that may be hard on your membrane as well. Your aquasafe should've come with a pressure switch that turns the water on and off automatically without letting the membrane dry out.

Thanks for all the great advice everyone.

Where could I buy a new regulator and membrane for this unit? It is going to be some time before I can actually buy anything at all (sooo broke), but when I can at least I will know where to go.