# RO water and tap water mix.



## kilnakorr (27 Jun 2020)

I'm thinking of getting and RO unit, and mix with tap water at roughly 50/50.
Question is how acvurate it has to be?
I REALLY don't want to mix it in containers and then pump it to the tank.
The easiest way is to fill tank with RO and tap water at the same time, but this obviously won't be an exact match everytime.
Could I just note down the TDS in tank after a while, and then just match that number with tap or RO water?


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## hypnogogia (27 Jun 2020)

Presumably you will have your RO in a container.  Easiest way is to fill with tap straight from tap to 50% of height taken out, and then top up with RO.  Hey presto, it’s an accurate 50:50 mix.


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## kilnakorr (27 Jun 2020)

hypnogogia said:


> Presumably you will have your RO in a container. Easiest way is to fill with tap straight from tap to 50% of height taken out, and then top up with RO. Hey presto, it’s an accurate 50:50 mix.


True, but don't want to store a 150 L container or 3 x 50L
Adding RO directly to the tank would be much simpler, but worried that amount will fluctuate.

But, I could just make a 'measuring' device, and fill 50% of water taken out, with tap and rest with RO.
Will make WC take longer, but would be pretty accurate.


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## hypnogogia (27 Jun 2020)

Ok, I hear that.  Are you suggesting filling up with RO as it’s produced?  That will be very slow though won’t it?


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## Wookii (27 Jun 2020)

Why is it that you don’t want to use a container? It would be far easier to manage.

Bear in mind that, depending on the size of your RO unit and the temperature and pressure of the incoming water supply, the RO production can be quite slow.

For example a 200GPD ‘pumped unit ‘ (so eliminating lower water pressure issues) would produce 40 litres in around 1.5-3 hours depending on temperature. 

So unless you get a really high output unit and install a mixer valve ahead of it to use heated and cold water feed (to maintain optimum temperature) the production rate is unlikely to be high enough to fill your tank while you wait during a water change.

It’d be far easier to have the RO unit run into a container and use a float valve to switch it off once full. That way you can just run it overnight so the container is full for when you need to use it. A simple pump can then lift it up into you tank when you are ready, and you can then top off your tank with your tap water.


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## kilnakorr (27 Jun 2020)

@hypnogogia @Wookii 
I need to produce around 75L RO.
I'm planning on a 600GPD unit that does a 1:1,5 RO/waste. So filling will take roughly an hour effectively (cold water and all).
If this could be added along with my tap water, it would great, but amounts won't be accurate from WC to WC.

Having a giant canister in the middle of the living room, with a hose running from the bathroom is not really an option.


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## hypnogogia (27 Jun 2020)

You could still fill 50% with tap first and then the remainder of your 50% percent with RO straight from the machine.  Just make sure that half the height of removed water from tank is replaced with tap and the other half with RO.


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## Witcher (27 Jun 2020)

Hey guys I'm just wondering where 50/50 is coming from? I think that the mixture must be strictly correlated with plants/animal needs we keep in the tank. For example if I have vast majority of plants and fish coming from let's say Pantanal region and my tap is for example 20dGH, cutting it with 50% or RO will give me 10dGH - that's way too much for lots of soft water liking plants and animals. On the other hand, If I will keep lots of high hardness liking plants (Microsorum/Vallis etc.) - 50/50 mixture may be suitable for them. 

BTW mixing RO with tap (to the desired hardness we have in our aquarium) in separate container is much better than pouring RO directly to the tank - if you have lots of shrimps for example, drastic change of water hardness may cause premature molting and if they are pregnant, they may also release their eggs too soon.


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## kilnakorr (27 Jun 2020)

Witcher said:


> Hey guys I'm just wondering where 50/50 is coming from? I think that the mixture must be strictly correlated with plants/animal needs we keep in the tank.


Just what I'm gonna start out with. Will still not be 'soft' water.


Witcher said:


> BTW mixing RO with tap (to the desired hardness we have in our aquarium) in separate container is much better than pouring RO directly to the tank


We can agree. But as already mentioned, for larger tanks (or married people) this isn't always possible


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## kilnakorr (28 Jun 2020)

Ok. Picking up my RO unit tomorrow.
What percentage(s) are a safe approach when switching to RO? 10% increase per water change, or is this to much?


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