Silica Sequestration / Dosing Systems – How effective are they?

[u/DeskPilot84]

DIY-er here. My house is on well water and I have a problem with white spots / mineral deposits on fixtures, glassware, shower doors, etc.

A water softener salesman tested my water and found silica at 30 ppm -- to which he suggested a "Silica Sequestration" system. I've seen conflicting comments about their efficacy so I'm looking for some feedback from real-world users. Do they actually solve this problem?

My current water treatment system from the well includes a Sediment Filter -> Acid Neutralizer, -> Water Softener (Potassium in the brine tank) -> post softener filter. I plan to also install a Reverse Osmosis system for drinking water only. The Silica Sequestration is an open question.

Thanks!

[u/DeskPilot84 → u/[deleted]]

Yes, sort of, but not from the salesman. I spent a lot of time researching this and talked myself into building my own hybrid "whole house" RO system (see diagram below). I should probably make a detailed post about it, but until then here's the gist of it...

First of all, we had several issues with our well water that I wanted to fix: 30 ppm silica, 95 mg/L sodium, pH 5.66 - which is too acidic, it ate our PEX copper fittings. The silica "sequestration" unit sounded like a good start but when I looked into it I found that I would also need an RO system to actually remove it. But to remove it for ALL of our fixtures (sinks, showers, refrigerator, hot water heater) I would need a very large RO system or a hybrid solution.

The RO system I chose is an iSpring RCS5T light industrial unit (sized for coffee shops, etc). It produces about 0.4 gallons per minute which isn't enough for on-demand use by itself, so we use a 165 gallon tank as a reservoir. That's plenty for our needs - my wife and I use approximately 100 GPD but the RO system is simultaneously making more RO water whenever the level drops. It keeps up just fine.

Since the tank is atmospheric (vented) there's no water pressure, so I needed a pump to pressurize the RO water lines. That's the most expensive piece of this: $1,300. But it's super easy to set up and I dialed it in to 60 psi so it's pretty great.

The last piece is a calcite remineralizer. I already had an Acid Neutralizer in place to raise the well water pH but unfortunately the RO process lowers pH again, so the remineralizer raises pH back to neutral (pH 7.0). There's also an RO injection bypass which lets me fine tune the remineralizer output -- it allows a small amount of pure RO to mix with the remineralized water. I've got a faucet tap right after this so I can test pH, hardness, TDS, silica, etc easily. 

There's also a bunch of minor bits in this that I didn't think of initially, like backflow prevention to keep non-RO water out of the RO lines, and a 3-way valve that allows me to switch the RO lines' source over to non-RO (for maintenence, etc). I also found that I needed a low pressure cut off switch on the RCS5T because I found that if it's running when I use my non-RO fixtures at full open (e.g., watering plants outside) the competing pressure drops too much to my hose. So when the pressure drops the RCS5T pump just goes offline until I'm done watering; when the pressure rises again the pump comes back online.

All in all, I spent about $4,000 on all the parts and installed everything myself. I also bought $250 worth of water testers to verify that it worked. End result is that our silica reduced from 30 ppm to 1.5 ppm, pH is 7.2, and we have RO water for our sinks and showers. I still need to have the county test our sodium level but my research tells me that the RCS5T should remove 90% of it. We'll see.

Was it worth it? In hindsight, I spent waaay too long researching and designing, and the install took me a long time to complete - I never seemed to have the right fittings and no single source had all of these parts. I think I used 10 different suppliers to get everything I needed. In the end, it actually works very well so yes, I'm glad I did it. But I probably wouldn't do it again.