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Reverse Osmosis System

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Lemonhands

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19 Apr 2022
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Bristol, UK
Hi all,

I am looking into purchasing and RO System so i can cut my water (I live in Bristol and so have very hard water). The fish i stock are hardwater fish but even by their standards my water is right up there, so i just want to essentially soft water down my very hard water enough to bring it in line and hopefully improve qol of my fishy friends. I would usually just go to my lfs but theyll probably only stock one model and so will push that, so thought id ask here before heading down there this week.

Does anyone have any recommendations? Is there anything else i should consider/know before buying an RO system?
 
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Aleman said:
I'll second both of those, and also throw Finest-Filters into the mix, (also known as finest aquatics). I built my own system from parts from all three of those (and also RO-Man), but I have researched RO units for years in my brewing roles, where they are actually not required for the vast majority of water conditions. If you have a variable water supply (like I do) and you need a stable supply, like we do as planted aquarists, then an RO unit can be really helpful.

1) get a pumped system, this ensures your production rate is pretty constant, and it's cheaper to do so at the beginning rather than add it on later.
2) capacity is measured in US gallons per day, which is only 3.875L rather than the UK's 4.5L, bear that in mind when determining your requirements ... also note that the capacity is measured at 20C, it falls off when water is cooler than this.
3) if you want pure water then you will need a 6 stage unit. This adds a DI stage after the membrane (and a carbon "taste" filter). I go from 130-150ppm TDS to 2ppm after the membrane, and the DI unit takes that to 0 ppm. If you are only "cutting" your supply water with a proportion of RO then a DI stage is not essential, but remember that ion selectivity is variable across the membrane. Silicates for example are only 65% rejected, whereas Calcium is 95-98% rejected.
4) expect to waste water. Domestic RO units run at anything from 1:2 to 1:4 permeate to brine, mine a dual (100GPD) membrane pumped setup is currently running at 1:1, and produces 0.8L of pure water a minute.

The good thing is that these units are modular, so adding an additional membrane to reduce waste water, or a DI unit can be done quite cheaply at a later date. This is mine attached to a 300L IBC container as storage. I'm currently building a surround for it.
View attachment 187437
I've just added that 7L Vyair DI resin chamber, and knocked the pre-filters off it's support.
Click to expand...
I would love to know how you've built this with a 1:1 ratio in mind. I was looking into this just recently and only just found out that 1:1 systems existed, my first RO unit had a reject rate over 5 😵‍💫
 
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Miniandy said:
I would love to know how you've built this with a 1:1 ratio in mind. I was looking into this just recently and only just found out that 1:1 systems existed, my first RO unit had a reject rate over 5 😵‍💫
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It's a series of compromises.

The dual membrane in series is one of the big keys to it. It's only something that you can do if you don't have a supply with crazily high TDS to start with, because the first membrane concentrates the ions before passing it to the second. This does shorten the life of the second membrane, but by how much, is yet to be seen.

A pumped system is essential, and ideally the pump will be overated for the membranes, and self regulating (Keeps a constant flow for the pressure)

Use a flow restrictor on the brine outflow that is lower rated than "ideal" for the membranes. My 100GPD membranes should be using a 1200mlM restrictor, but I used a 800mlM initially, and got just below 2:1. I swapped it for a 500mlM, and was running at around 1.1:1. I have swapped down to a 300mlM restrictor and that has brought it right down. However, as that happens the TDS of the Permeate/product line from the membrane increases. In my case at 800mlM I had 0ppm out of the membranes, at 500mlM it was 1-2ppm, and it's now 4ppm with the 300mlM unit. This has a cost implication as the DI resin is exhausted faster. I'll probably drop back down to 500mlM especially if I can find a Auto flush kit with that rating.
 
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MichaelJ said:
@Lemonhands OK, I see. Well, if your doing 30% of 345L/wk thats ~100L/wk. If you only seek to cut say 5 GH off from say 15 GH you need about 33L of RO water weekly the rest being your tap. The problem people usually runs into is storage of the RO water so you have to factor that in. I got the 100GPD RO Buddie with the optional DI cartridge (the water comes in at 270 ppm and out at 2 ppm). I am using 100% remineralized RO+DI water in both my 150 L tanks with weekly ~40% WC. Making about 120 L/wk - its manageable, but I wouldn't want to deal with more than that.

The efficiency is a function of temperature and water pressure:

View attachment 187460


Cheers,
Michael
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I'm considering to have a RO system set up as well. Storage of the RO definitely can be an issue.
 
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Waste ratio: Though it's possible to reduce the waste ratio to 1:1, it will seriously degrade membrane life to the point where it's not economical (unless you have zero KH water). I personally don't think running dual membranes in series is worth it. By ensuring adequate pressure (up to 75psi) and using a flow restrictor slightly lower than the flow rate for the system, I can get the ratio down to 1:2.5. This is more than manageable for me to reuse all of it. I use it for filling the toilet tank primarily, but it can also be used in the laundry, for watering plants, etc.

Booster pump: Before investing in one, make sure you know the the pressure in your water line. Mine produces 90psi, which is too high for the pressure rating on the housings. I use a pressure regulator to decrease the pressure to 75psi.

Storage: I use 5-gallon carboys to store my water, since I don't have large volumes. Those with bigger tanks typically store in a Brute trash bucket. If you're storing for a long period of time, however, just be aware that the RO/RODI unit should be run at least every two weeks to keep the resin (if you're using one) and membrane wet. Otherwise, you need to remove the membrane and cartridge and store it in the refrigerator in a sealed bag with water.
 
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Lemonhands said:
I am looking into purchasing and RO System so i can cut my water (I live in Bristol and so have very hard water).
Click to expand...

Osmotics:

1652380986162.jpeg

Sediment filter, GAC filter, carbon block. 3x RO membranes in series with booster pump:

1652381053042.jpeg

This takes Cambridgeshire Tap from 400-500 TDS down to 4-6 TDS.

Followed by two DI resin chambers this brings the 4-6 TDS down to 0 TDS.

After 15 months of service producing 300 litres per week the performance of the RO membranes is unaffected. It produces 1:1 waste to product at a rate of 50 litres per hour regardless of starting temp for all intents and purposes. The waste goes into rain barrels and will feed your garden year round.

Change out filters (sediment and carbon) every 6 to 9 months. DI resin is most effectively used by using regular DI resin for 90% of the cartridge and the last 10% colour changing. Changing DI resin every 2 months here.

You can wire in a TDS meter:

1652381567183.jpeg

Layers of colour changing DI resin is good for early warning though.

The changing of filters on a schedule goes a long way to preserving the membranes. Even more importantly though, flushing your membranes for a couple of minutes prior and post producing product avoids a lot of cost. All Osmotics units come with a flush valve so this is very simple to do.

Tip: either disconnect the DI resin when flushing the main unit or fit a John Guest valve to direct flow to preserve DI resin. There is no need for DI resin to be involved when flushing RO membranes.
 
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Luckily I am not on a water meter, but for the sake of not wasting water I purchased and extra membrane. I didn't realise that i wasn't able to post a video on my ast response, but I will post a picture when I next set it up again
 
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judith97 said:
By the way, I found a website it may include the thing that you've warned me out. Here: 10 Best Countertop Reverse Osmosis Systems Of 2024
Would you spend a little time on reading this for me? Thanks
Click to expand...

I did wonder if you were an SEO spammer before I replied, but I took the chance! Oh well!! Reported!
 
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Hi
It depends on the pressure from the mains and if it is a new RO filter membrane.
I can produce 1 litre in approximately 8/10 minutes.
 
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