Kessil

Searching for a better RO system

svreef

BOD
Staff member
I have had an iSpring RO500 for several months now. It claims a 2:1 product/waste ratio (I don't know how) and 500 GPD. It comes with a neat faucet that shows the TDS of the product water. But, I'm not very happy with it and I spent too much on it to not be happy. The output TDS fluctuates between 100 and 500 which seems ridiculous and eats up the DI resin downstream very quickly. You can clearly see the TDS creep: you run for a minute and the TDS is 100, then it jumps to 500 and starts climbing back down slowly. It definitely has a booster pump, but I don't know whether it auto flushes (it does flush when I cycle power). Also, the replacement cartridges are expensive.

I think I can do better but it is such a confusing subject.

I'm on well water which seems to have > 1000 TDS. I have a whole house sediment filter and water softener.

Would I get lower TDS out of RO if I switch to a system that has a Smart Buddie and feeds into an RO tank, say 20 gallons. That way, the RO tank is filled once a day automatically by switching on the smart buddie. Switching it on would also run its auto-flush. My kitchen faucet and fridge would take water out of that tank and it would also feed my DI stages when I need DI water.

Space and ugliness of installation are not an issue.

I'm thinking of this one: https://www.uswatersystems.com/us-w...e-pressure-ro-system-with-20-pre-filters.html
Adding the smart buddie and re-plumbing the two membranes to be in series.
 

Rostato

Supporting Member
Are you talking for drinking water? That iospring definitely isn’t made to handle highly dirty water.
 

svreef

BOD
Staff member
Are you talking for drinking water? That iospring definitely isn’t made to handle highly dirty water.
Both drinking and DI. If that system isn’t made to handle dirty water, then what is? How do you get the most TDS out of the water before DI? More membranes? More pressure? Better membranes? I’m stumped.
 

Meshmez

Supporting Member
You might benefit from running a couple sediment filters and a couple carbon before your ro membrane. But 1000 tds is rough...

You say it goes from 100 to 500 then back down. Does it go back down to 100 and stay steady?
 

borker

Supporting Member
I just had a thread on this. There were some recs.

Most people are big on the BRS systems—for yours you’d do the 6 stage they suggested but they’re expensive.


Sent from my iPhone using Tapatalk
 

Rostato

Supporting Member
Both drinking and DI. If that system isn’t made to handle dirty water, then what is? How do you get the most TDS out of the water before DI? More membranes? More pressure? Better membranes? I’m stumped.
It’s sediment filters are not designed to clean up water that dirty. Your on the right track with that is water systems one. I would do two large sediment filters, and a large carbon filter to filter out any other gunk. Then the RO membranes will be better protected.
 

Rostato

Supporting Member
You might benefit from running a couple sediment filters and a couple carbon before your ro membrane. But 1000 tds is rough...

You say it goes from 100 to 500 then back down. Does it go back down to 100 and stay steady?
Yeah, you need the large sediment filters andyou’ll probably need to replace them often. Well water was nasty in GA where I come from. It was literally clay orange in color
 

svreef

BOD
Staff member
Sediment filters don’t lower TDS. Dissolved solids flow right through them. They remove other solids and protect the membrane.

I recently added a very big, whole house sediment filter.

I know that after I power cycle my current system it flushes and the TDS after that is < 10. Sometimes, it is 1.
 

Rostato

Supporting Member
I never said the sediment filters would take out tds. I said they would get all the crud out before your membrane... either way, that’s weird. I got nothing then.
 
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NanoCrazed

Supporting Member
I have the ispring rst 500 gpd setup. Seems Ok... suppose to be 1:1. The RO is 80-85% efficient I believe.

So, on 1000tds, you'd get abou 150tds on the output (which btw is the ideal target for drinking water based on what I've read). I have a mixed DI catridge tapped before the last stage carbon filter... and it does the trick on city water. (I have a separate RODI setup for majority of tank needs but this is my emergency backup).

Have you considered using a 3 stage DI setup after the RO filter?
 

jccaclimber

Supporting Member
I'm impressed. I had a consistent mid 400's TDS in a previous place I lived and I thought it was hard on my RO unit. On the plus side, you don't need to deal with chloramine like the rest of us.

If you're seeing a TDS of 500 coming out of your membrane one of the following is happening:
It's high CO2 in the water. I've seen this in well water once before where the CO2 was so high the water tasted bitter. This was in a house at elevation in the desert, so I'm guessing they had a very deep well. If this is your issue then your options are either put up with it, or aerate it in one tank, then use a booster pump or gravity to feed it through the DI after it off gasses.

500 GPD is really high for an RO system. That thing must have an enormous membrane.

I'm going to preface this with the fact that I don't know the food grade suitability of the components I'm going to recommend. I know how to get 0 TDS out of it, but I don't know much about suitability for human consumption.
If I was building one from scratch for your sort of system I would:
1. Consider if you really want 500 GPD capacity. I'm used to seeing drinking water systems at 25 to 75 GPD. I'm going to assume for this that you don't need more than 200 GPD.
2. Put in an additional set of sediment filters. If your house filter is say a 5 µm I'd run a 1 µm. Not sure I'd add the 0.2 µm filter, but it certainly wouldn't hurt.
3. If you're going to carbon filter a large portion of your house water, put a chloramine monster in and change it annually. If it's just this then put a standard carbon block in.
4. Booster pump right before the membrane. I'm used to Aquatecs, but the RO Smart Buddy might be a cheaper overall package.
5. Pay Spectrapure for 1 (or 2) of their tested 99% rejection rate 90 GPD membranes. If you really want to get your waste ratio down (I'm not sure what the effective cost of your well water is) run them in series (waste from 1 is the inlet to 2, product lines merge). They're a bit more expensive, but with your TDS they'll pay for themselves in DI resin savings.
6. Either put in a flush valve that you exercise regularly, or get one that auto flushes.
7. Confirm your high TDS isn't a function of dissolved gasses by aerating it (blender in 30 second intervals and checking TDS before/after does this nicely, as does letting it sit overnight or running an airstone in it for a while).
8. Determine if the TDS that does pass the membrane is best absorbed with anion or cation resin. Put 2 of these in front, and a third of the other (ie it might be 2 anion and 1 cation). You could also go 1 anion/cation and a mixed bed.
9. Put in an accumulator so that it makes your drinking water in advance rather than as you fill the cup.
10. If you don't already have them as a function of one of the above systems, make sure you have a mechanism (float valve, pressure switch, whatever) that shuts off the output, including the waste water and.
11. You'll want inline TDS meters to gauge filter condition.

As a note, I've had my RO run as good as 1:1 in the past, but it definitely would not do so if it was fed with 1000 TDS water. If I remember correctly that's going to put something like an extra 10 PSI of osmotic pressure, so you're not going to get the same rejection rate or throughput (pick one) of a system rated at 200 TDS softened water. You can play with your output ratio a bit by changing the temperature and pressure of the system, but I haven't done much of this to determine where the knee in the curve is.

Obviously this doesn't perfectly match a pre-made system, but you could get 90% of the way there with one from BRS or a few other places and tack on the extra parts you want pretty easily.

For those curious and wanting to chase more costly solutions, there are some other things like flushing your membrane with product water and not just straight bypassing the output restrictor. Mine does this, but I don't actually know what this does for membrane life. This is slightly inconvenient as it requires the unit to be lower than the low water switch in the reservoir. I'm not sure how that would play if I had it feeding into an accumulator.
 
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