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RO & Tap Water Changes Best Way

Daniel

Daniel

Member
Joined
9 Dec 2013
Messages
97
Hey everyone,

So I'm in process of setting up my new 350L tank and as I have an RO unit set up in my loft for my reef tank I want to make use of it for my planted tank.

The loft sits in the extension above the kitchen with the loft hatch virtually above the new tank.

I want to cut my RO with 50/50 tap. I have a 100L ro storage tank in the loft and wanted to drain it during water changes straight in to the tank and then top up the remainder with tap and prime straight in the tank. Would this be okay or should I mix the RO and tap before adding it to the tank?

It's a bit of a PITA but I could drain the RO from the loft tank to another container, mix in the tap and then pump in to the tank but would rather make it more painless if possible.

Any thoughts on my plan would be greatly received.

Thanks, Dan.
 
I would add the prime to the tank (add enough for the full volume) and then add the tap and RO at the same time - you'll need to adjust the tap to roughly the same flow rate. You can use a TDS pen to monitor and make sure you get your rough 50/50. Depending on your occupants and the amount of water you change you could cause them problems going from medium hardness to very soft and back again in a short space of time as it mucks up their osmotic regulation.
 
Thanks for your input. It's a good idea but won't it be hard to get the 50/50 mix like that? The other solution would be to drain away 100 litres (example volume) then mix 50L of RO and 50L of tap and prime in a secondary container and then pump it in? The other suggested way I may get the flow rates off and loose a lot of RO in the process of setting up prior to topping up the tank?


Sent from my iPhone using Tapatalk
 
Hi Daniel
You probably better trying to split the Tap water source into 2 outlets!
Obviously you will have your RO line with Tapwater going into the RO unit, split this into two!
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You could add a OFF/ON valve to the Tapwater line...;)
Run this straight into your tank add dechlorinator first!

IfcxCEJPkJQHaHa&w=199&h=200&c=7&o=5&dpr=1.25&pid=1.jpg

hoggie
 
That's a good idea, I'll definitely split the feed line so that I have a RO and a tap source, however that still doesn't solve mixing it in the tank? I'd still have to get the levels just right still and adjust the flow as the tap water line will come out faster as it will be under pressure even though it's the same diameter line?


Sent from my iPhone using Tapatalk
 
Hi Daniel
I wouldn't be to precise...about mixing!
Remove 50% tank water.....then add 25% RO water then add 25% Tap water!
Where are you based?
This is the way I would re-fill the aquarium as Tap water can be very cold in the UK.....especially this time of year!
As you have stored RO this water temperature will be higher than tap!
hoggie
 
Hi all,
Daniel said:
however that still doesn't solve mixing it in the tank?
Click to expand...
I'd approach the problem in a different way, and use tank water conductivity as a measure of the water mix.

You would need to measure the tank conductivity (after a 50:50 water change?) to give you a datum value, and then on the next water change add in about the right volume of tap to the tank (doesn't have to be an exact volume) with the water conditioner already added to the tank. Then pour in the RO, and re-measure the conductivity. You just need a ball park figure, say 50 microS either way.

cheers Darrel
 
I assume you still have your marine tank, thus will still need RO water.

Idea 1.
upload_2018-9-27_10-55-39.png

1. Put another tank in loft, the mixing tank.
2. Fill RO tank.
3. Open connecting valve to allow 50% of the water into the 2nd tank.
4. Close the valve.
5. Fill the mixing tank to the top with tap water (and dechlorinator ?). (add heater to warm ???).
6. Drain to planted tank.

Idea 2.
upload_2018-9-27_10-57-45.png

Put a syphon tube, going down to 50% depth in the RO tank.
Syphon 50% of RO water out into tank, fill with tap water & dechlorinator.

All methods have great potential for interesting failure modes ie waterfalls from the loft, to take care and plan carefully.

Or implement my example number 2 on using a PLC ?
https://www.ukaps.org/forum/threads/how-to-use-a-plc-to-control-your-fish-tank.42993/
 
Daniel said:
Thanks for your input. It's a good idea but won't it be hard to get the 50/50 mix like that? The other solution would be to drain away 100 litres (example volume) then mix 50L of RO and 50L of tap and prime in a secondary container and then pump it in? The other suggested way I may get the flow rates off and loose a lot of RO in the process of setting up prior to topping up the tank?
Click to expand...

I think you could experiment a bit and work it out. You could time the flow rate of your RO and then adjust the tap to generate the the same flow. So time how long it takes to fill a 5L bucket with RO, then experiment with the tap flow rate to fill the same bucket at the same speed. You only need it roughly right. Then use a TDS pen to monitor the mix as it fills.

So, if your tap is 400 TDS, your RO is 0 and your tank is 300, if you change 50% of the water with a 50/50 mix you know your new TDS should be 250. Eyeball it with the flow until it's nearly full, test it and then add a bit more tap or RO to tweak either way if necessary.
 
Thanks guys all are good ideas. So basically as long as we measure the TDS/EC then adding straight to the tank shouldn't be a problem?

I had thought along similar lines as Ian_M about having a mixing station of sorts in the loft (a bit like many plans online for salt mixing stations for reefing). However, I'm still trying to keep it more simple if possible. I feel if we make things more complicated than they need to be we start to enjoy the hobby less.

So just going straight in to the tank with 50% tap then adding 50% from the RO reservoir in to tank is the way to go if possible. I guess I will end up with a similar TDS/EC reading after the water change as I had before the change, but might fluctuations happen whilst adding the tap then RO I guess?


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The fluctuations should be quite minimal I would have thought due to the dilution factor in the tank water as you are only changing 50% of the water in your tank so the 50% water left in your tank should give stability as you do the water change?
 
Daniel said:
So just going straight in to the tank with 50% tap then adding 50% from the RO reservoir in to tank is the way to go if possible. I guess I will end up with a similar TDS/EC reading after the water change as I had before the change, but might fluctuations happen whilst adding the tap then RO I guess?
Click to expand...

Yes, you'll end up with a similar (although in real conditions slightly lower as the tank is usually higher than a clean mix due to ferts/fish waste etc.) post water change. You can calculate the exact number though if you know the tanks TDS, new water TDS and portion changed. If you do one and then the other you are going to fluctuate it during the process How much depends on your tank, tap and percent water change. The higher your tap TDS (more difference from RO) the more fluctuation in real terms i.e.

Start Tank TDS : 200
Add Tap (400) Tank TDS: 300
Add RO (0) Tank TDS: 200
Actual change +-100

Start Tank TDS : 100
Add Tap (200) Tank TDS: 150
Add RO (0) Tank TDS: 100
Actual change +-50

If you don't want to add both at once, you can reduce the fluctuation by alternating, the more you alternate the less the real change. So roughly add half the RO, half the tap, the rest of the RO, the rest of the tap. Again use the TDS/EC to confirm your eye-balling and tweak at the end.
 
The next question I am going to ask is....why are you going to all the effort & cost of using RO water in a planted tank ?

Reasons for not using/requiring RO water.
- Extra complexity & time & effort at weekly water change time.
- Most plants and fish don't care about water hardness & minerals. In fact minerals in tap water is in fact a major positive point for using tap water.
- Cost.
- Having hardwater (dKH above 8) is generally useful to provide a degree CO2 buffering, to prevent pH swings (pH crash).
- Having hardwater (dKH above 8) enables pH meters and test kits (if you insist on using test kits) to get more meaningful readings.
- Having to test RO water for ammonia & chlorine before use. This is one time a test kit will give a reliable reading. Yes this is true RO systems DO NOT 100% guarantee chlorine removal and ammonia removal from chloramine, so RO water must be dosed with dechlorinator before use in a planted tank (or have a 100% top notch RO system). Not generally done in marine world, as RO water is often stored and salted before use which out gasses the chlorine and ammonia if present. This is an issue that needs consideration in planted tank world using RO.

Fish don't care about hard water.
https://www.ukaps.org/forum/threads...-aquascape-with-hard-water.52248/#post-518021
Nor do plants.
https://www.ukaps.org/forum/threads...of-high-kh-on-plant-growth.51378/#post-504774

My water is 22dKH from the tap and I have no issues growing plants and breeding fish.

So for a planted tank, I have never been convinced that RO water is a requirement for keeping beautiful plants and fish. Much much much much more important is CO2 flow and distribution & ferts and light control.
 
Thanks Ian, those threads make for interesting reading. I was going to use RO water purely because I already had it for my reef set up and thought softer water would be better (excuse my ignorance - it's been a few years since I've had a planted tank!) So perhaps I am making it far more complicated than it needs to be!?!

I'm in Surrey and although the tap water is hard, it's not as bad as I thought it would be. I took some readings last night... NO3=40mg/l, GH=7d, KH=10d, PH=7.4. So perhaps I should keep it really simple... add prime, add tap, done!!!
 
If mine was GH7 I'd just use tap :) That's what I mix my RO back up to. Pure RO is good for top ups though :)
 
Must agree with Ian too. My tap water is around GH 9 if i rember correctly:). When i used RO to cut the tap water around 50/50 because I already had a RO unit for the effort involved I saw little or no difference. Made water changes a PITA to be honest.
Now I just used declorinated tap water.
By all means give it a try seems to work for some:).
 
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