At my wits end: DI Nightmare

Miami Reef · Mar 28, 2023

@Randy Holmes-Farley @Lbrdsoxfan

I ordered the Dow Chemical 100GPD (98% rejection rate) membrane from bulk reef supply: https://www.bulkreefsupply.com/100-gpd-membrane-dow-filmtec.html

It came today. (Along with the prepackaged di resin from BRS)

My tap water TDS is 178ppm.

(My sediment and carbon blocks were changed 2 weeks ago, rinsed, and hardly used).

After running the new membrane for almost 30 min, the initial tds went from 8ppm to 11ppm.

Before anyone asks, I even changed my inline tds monitors a few weeks ago because they were old, and I questioned the readings.

Is it normal that my tds readings after the membrane are still pretty high? The pressure going into the membrane is 80psi with my booster pump (I always use my booster pump).

Miami Reef · Mar 28, 2023

Now TDS is going to 12ppm. It’s only going higher the longer it rinses out.

In my previous experience, allowing the new membrane to soak in the system (without running) made the TDS after the membrane lower. Running it had no effect on lowering the higher TDS from a new membrane.

Does this sound like a normal process that happens with membranes to you guys?

LandLockedJones · Mar 28, 2023

I’m no expert, but check the water reports for the county. Maybe send off an icp test that will test your DI water source and see if there is anything bypassing the system it’s just not designed to capture. Total dissolved solids can really be anything with an electrical charge if I’m not mistaken. Which could be a ton of different things.

Also how are you measuring? As in what tools; tds pen in a barrel of produced water, or digital probe style sensors?

If you’re using the digital gauges on the brs units, it may be a mechanical issue. I might would consider starting with removing the tds probes and inspecting them. Could be dirty or fouled. Just be sure to reinstall them so water passes through the goal posts. Or it will not get proper readings.

Or turn them sideways and live forever in denial…sorry that’s not helpful haha

Buckeye Hydro · May 17, 2023

Is your membrane installed backwards?

Do you have an internal crack in the cup wall into which the membrane seats?

t5Nitro · May 17, 2023

Like everyone else is saying, this is a problem with your membrane and not your resin.

Mine does the exact same thing, though not quite as fast. Brand new dual membranes make about 60 to 100 gallons of water with post membrane TDS of 3, then it creeps up to 10. Once it's there, it starts burning through the DI resin.

I never did get a great answer. I was hopeful to find something in your thread and will follow to see if you figure anything out. I also got membranes from BRS.

Miami Reef · May 17, 2023

The issue was fixed ever since I purchased the BRS membrane and prepacked resin.

t5Nitro · May 17, 2023

The resin shouldn't factor in at all to your membranes rejection rate. Must have been your new brs membrane by itself. Glad that worked.

Miami Reef · May 17, 2023

t5Nitro said:
The resin shouldn't factor in at all to your membranes rejection rate. Must have been your new brs membrane by itself. Glad that worked.

I know, but even with some TDS, I wasn‘t getting 0tds after a new di resin that I packed myself.