RO unit on Well water

[Mady4real]

I just installed the RO unit on my well water of above 900 TDS the Unit lowers the TDS to 60 TDS.. but i am skeptical to go for DI since as far as i read the forums 60 tds will burn DI resins like wildfire... Is there any way to reduce TDS more? I hav 75gpd system with 100gpd membrane...

 

[josephxsxn]

What's the pressure on your inlet to the ro? I also am on well water and I got really poor performance until I installed a booster pump to get to 90psi inlet pressure to the RO system. I get about 4tds before my di.

I agree 90tds will eat your di.

 

[Dkeller_nc]

Yes. With "liquid rock" tap water of 900 ppm, it may be well worth the expense and trouble of installing a whole-house water softener. Not only will that preserve your plumbing and drastically cut down on the amount of scale that you have to clean out of the bathroom appliances, converting the likely high content of divalent cations (Ca, Mn, etc...) and sulfates/carbonates to sodium chloride will make your RO membrane dramatically more efficient, and will prevent it from rapidly scaling with insoluble precipitates that are very likely to form on the upstream membrane surfaces.

After you do this, I suspect that you will find that DI resin will last quite a while.

 

[Mady4real]

What's the pressure on your inlet to the ro? I also am on well water and I got really poor performance until I installed a booster pump to get to 90psi inlet pressure to the RO system. I get about 4tds before my di.

I agree 90tds will eat your di.

That i will hav to check i am not sure of the pressure.. what if i went DI route with 60 tds approx how much gallon before it will burn?

 

[Dkeller_nc]

This particular website suggests that the mixed cation/anion resin that they supply has a capacity of 12 kilograins per cubic foot of resin. In the note at the bottom, they state that 1 grain/gal = 17.1 ppm as calcium carbonate.

In your case, you've 60ppm after the RO unit. Assuming for the purposes of calculation that it's all calcium carbonate, then your water is 60/17.1 = 3.5 grains/gallon. You can therefore assume that you'll be able to process 12,000/3.5 = 3,428 gallons per cubic foot of resin. Obviously, the average container of resin in a standard water filtration holder is no where near a cubic foot. Bulk reef supply suggests that the most popular size for a DI cartridge is 2.5" x 10". Doing the math, you come up with a volume for that cartridge of 0.25 liters. Since a cubic foot is 28.3 liters, you finally arrive at 3,428 gal/cubic foot * (1 cu ft/ 28.3 L) * 0.25 L = 30.3 gallons.

There's a lot of assumptions and round-offs in that calculation, but even if it's too conservative by a factor of 2X, it probably makes the most sense to get a water softener for your home.

 

[Mady4real]

.. delete post

 

[Mady4real]

This particular website suggests that the mixed cation/anion resin that they supply has a capacity of 12 kilograins per cubic foot of resin. In the note at the bottom, they state that 1 grain/gal = 17.1 ppm as calcium carbonate.

In your case, you've 60ppm after the RO unit. Assuming for the purposes of calculation that it's all calcium carbonate, then your water is 60/17.1 = 3.5 grains/gallon. You can therefore assume that you'll be able to process 12,000/3.5 = 3,428 gallons per cubic foot of resin. Obviously, the average container of resin in a standard water filtration holder is no where near a cubic foot. Bulk reef supply suggests that the most popular size for a DI cartridge is 2.5" x 10". Doing the math, you come up with a volume for that cartridge of 0.25 liters. Since a cubic foot is 28.3 liters, you finally arrive at 3,428 gal/cubic foot * (1 cu ft/ 28.3 L) * 0.25 L = 30.3 gallons.

There's a lot of assumptions and round-offs in that calculation, but even if it's too conservative by a factor of 2X, it probably makes the most sense to get a water softener for your home.

dang! But water softener is too big of an investment where i live.. What about if i pass the 60TDS water through second membrane along with a second pump? Will that reduce TDS so it can go through the DI? This may require some modifications bt if it’s doable i will go for this route!!

 

[josephxsxn]

I imagine you could buy a second ro unit to use the output of the first on therefore reducing it enough to pass to the DI.

Does your unit have a control for waste water? Like 1:1 or 1:2. With such high TDS I speculate that the RO membrane will go bad much faster. On mine the 1:2 makes more waste water but protects the membrane for longer.

 

[Dkeller_nc]

dang! But water softener is too big of an investment where i live.. What about if i pass the 60TDS water through second membrane along with a second pump? Will that reduce TDS so it can go through the DI? This may require some modifications but if it’s doable i will go for this route!!

You can, but there's a strong likelihood that your RO membranes will scale over. That can be controlled with a chemical injection pump and an anti-fouling chemical mixture, but that's getting awfully complicated for a hobbyist system. One can also religiously apply an RO membrane flushing procedure, either manually through a valve like this, or with an automated system, but with 900 ppm TDS in the feed water, that might not provide much benefit.

I would guess that you will eventually decide that installing a water softener is the cheapest route when the cost of RO membranes and DI resin is calculated out. That might be years before a break-even on the $600 or so for a whole-house water softener if you have a single, 20g reef tank, and may be a few months before break-even if you've a 100 gallon tank.

 

[Weasel1960]

Folks here need to be a little more aware of where our reefing friends are from. Water softeners are not always readily available or as cheaply priced in other countries as here in the US.

Mady you might want to try pre filtering your water through progressively finer filters, down to 60 or 100 microns, before going through your RO unit. Yes a second RO unit may also help and as suggested a higher waste factor may make your membranes last longer. Then test your TDS coming out to see if you got your values any lower. You may also need a booster pump to keep the pressure up going through multiple filters. Any chance you can distill large quantities of your well water first, store that, then pump the distilled water thru your RO. Distilling still won’t catch everything but may leave some of the heavier solids behind so the RO wouldn’t have to deal with them.

 

[92Miata]

Folks here need to be a little more aware of where our reefing friends are from. Water softeners are not always readily available or as cheaply priced in other countries as here in the US.

Mady you might want to try pre filtering your water through progressively finer filters, down to 60 or 100 microns, before going through your RO unit. Yes a second RO unit may also help and as suggested a higher waste factor may make your membranes last longer. Then test your TDS coming out to see if you got your values any lower. You may also need a booster pump to keep the pressure up going through multiple filters. Any chance you can distill large quantities of your well water first, store that, then pump the distilled water thru your RO. Distilling still won’t catch everything but may leave some of the heavier solids behind so the RO wouldn’t have to deal with them.

About 2 minutes of Google searching and I found single tank water softeners in pakistan for the equivalent of $1000 - which Is a little pricier than the US, but reasonable. $700-800 is about what we'd pay.


OP - figure you're going to be paying close to a dollar a gallon in prefilters, di, etc if you don't do something.

How much water do you make?

 

[KStatefan]

What are the specs on your membrane? The older filmtech 100 gpd membranes only had a 90% rejection rate. With that high of TDS I would not go less then 4:1 waste to good water. You could run you output thru another membrane also but i would look a a 99% rejection membrane and make sure you are at 80psi first.

 

[chipmunkofdoom2]

I would not go with the second membrane. With the high mineral levels in your water you'd burn one or both out in very short order.

I'd go with what KStatefan said. Your best bet is going to be tuning your system to run at maximum efficiency. If you get your pressure up and get a quality 99%+ rejection rate membrane, your final TDS should be around 9-10 ppm, not 60ppm. As mentioned you'll want to make sure to keep your ratio to 4:1. At 900ppm TDS, you don't have any room to be playing around with lower ratios. Lower brine flow will clog your membrane pretty quickly.

I'd also keep close watch on your sediment filter. Different wells have different particulate levels, some high, some low. Keeping your sediment filter clear and the pressure up is going to be critical to producing low TDS permeate in your situation.

 

[Mady4real]

I discussed my issue with few reefing experts here and the only solution is going for a second membrane..
this is how it will look like, first membrane with 180gpd and second membrane of 100gpd with booster pump that will reduce the tds to less than 5 and then to DI for zero.. costing me around 200dollar for the setup and then the yearly consumables and maintenance cost, so given my current requirement of just around 120 liter per month i think its not cost effective.. since same amount of distilled water is costing me around 3.5 usd.. i think ill drop my plan of RODI setup till tank ugrade.. Thank u a for ur help

 

[ca1ore]

Agree to get a better RO membrane. I'm on well, 455 into the RO stage, 5-7 out. DI lasts a while.

 

[K7BMG]

If you have the ability to have the water analyzed will be a help to you.

 

[Will Wohlers]

Im on a well in the mountains of western nc and man I feel bad for you guys. I hit 5 tds straight out of the faucet. I guess im extremely lucky.

 

[K7BMG]

Right from my well I am at 180-190.
I would use it from the water softener but alas the softener is in the house and my tank and fish room are located in the detached shop so that wont work.