RODI Won't hit rejection rates

[BlueZreef]

Idk what's wrong...I swear I've tried everything at this point!

Here's what I have setup:

Pre filter culligan filter -> aquatec 8800 booster-> 3x carbon blocks 1 micron and one is .5 micron I think from BRS -> 100 gpd Dow filmtec -> 3 DI canisters

I just swapped to the 100 gpd hoping the rejection would be better...it not! From the tap reading is 120ish. After membrane only getting down to like 7-8. DI resin takes it to 0 but I burn through resin like no tomorrow!

I was using a 150gpd Axeon membrane and it was only getting it down to like 8-10 TDS. Pre filters from BrS are less than a month old.

I have an 800cc fast flush for the 100 gpd and was using a 1200 with the 150gpd. Pressure with booster is at 85 psi. I always flush for at least 15 mins if not more prior to starting.

What's wrong here? 98% rejection should put my output around 4 tds.

I checked my waste ratio with the 100gpd and its 4.3/1, seems perfect...?

I burn through tons of resin, like a whole canister makes me roughly 60 gals...some people say their resin lasts for 6+ months...I wish! HELP

 

[gus6464]

You want the booster after the carbon blocks before the RO membrane. Try that and see what you get.

sediment -> carbon -> booster -> ro -> di

 

[Joey waid]

Rejection rates are always high. If I was you I would get a tds meter and not worry about the color of the resin. I see you have a meter sorry. I would do what the post above me said. My resin changes color fast but the tds almost reads zero.

 

[Saltine]

Free bump, i use spectrapure and my TDS going in is around 170, and it comes out at 1 before DI. It's only a 4 stage (including the DI). So sediment, carbon, membrane take out 98-99%.

 

[DLHDesign]

Pressure with booster is at 85 psi.

That sounds like it's too high to me. The membranes have an ideal pressure rating; below OR above it will cause them to loose efficiency (for different reasons, but the result is effectively the same). The 100gpd membranes that you have are rated for 50psi. You could either reduce your incoming pressure or upgrade to the 150gpd membranes; which look for pressures closer to what you have. You'll still be high (65psi is ideal; I run mine at 70psi with good results), but closer, at least.

 

[BlueZreef]

I'll have to get a few fittings to put my booster pump between the carbon blocks and membrane. I'll work on moving it and see if it helps, not sure how much that will matter though?

I don't think the pressure is an issue honestly, I've read people running pressure over 100 psi with near perfect 1 TDS output. I also already had a 150gpd and the rejection was worse.

 

[gus6464]

When I bought my booster kit from spectrapure Jeremy asked me what I was going to run the psi at and he cut the flow restrictor based on that. So increasing psi isn't really going to do anything if the flow restrictor doesn't account for that I would think.

 

[DLHDesign]

I'll work on moving it and see if it helps, not sure how much that will matter though?

I don't imagine it will make any difference either - the effectiveness of carbon is based on contact time; not pressure. Whether the booster pump is ahead of the carbon or behind it, the flow rate will be the same.

I've read people running pressure over 100 psi with near perfect 1 TDS output.

Keep in mind that practically everyone's water is different. This means that different methods/membranes will have a different impact in each person's water. Unless you are comparing your results to that of someone else with the same water source, then exact comparisons are difficult.

I also already had a 150gpd and the rejection was worse.

Note that if these are the 150gpd membranes you had, they are rated for 150psi.

What temperature is your water at? Temperature comes into play when it comes to the membranes.

Do you drain your waste water into a container, by chance? I do, and noticed that when my waste-water container fills up, my resin burn rate increases significantly (I have an auto-shut off for when this happens, but I had it hooked up wrong).

My TDS pre-DI is 9, which is then run through two DI canisters. My burn rate is what I would expect - about 100gal per canister.

 

[BlueZreef]

I suppose my DI burn is similar to yours with a similar TDS out.

Water has been very cold as of late due to the weather. I try not to run the unit as it's in my garage if it's not above freezing.

The 150gpd unit had a max pressure of 150psi, not operating psi, 50psi min.