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RO water temp in

Luvlyjub

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So I have just purchased a 3 stage RO unit and can see the disclaimer that volume produced and quality subject to incoming pressure and an ambient temperature of 25degC.

I expect to only use the unit only every couple of weeks and store RO produced I have not directly connected to cold feed. As I have a mixer tap diverter I can connect to this using a 1/2 inch to 1/4 inch push fit for the RO tubing inflow to unit I can therefore control temperature of water coming in. So has anyone experience of doing this and does it help or matter?
 

GHNelson

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Not an expert on RO performance regarding temperature!
I wouldn't bother, just use cold.
If your going to store it use a heater to increase the temperature in the container before you use it!
Or mix with luke warm tapwater!
 

Luvlyjub

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Since posting I thought I would test as I have been running in unit for over 3 hours as suggested with all water to waste.

My TDS is over 500 from tap and when I tested it was 35 after RO that was probably not an issue for my use but expected better - although I appreciate I am not using an extra DI stage.

So, I have just tweaked the mixer to increase temp and my TDS reading is now 19 on the clean water that is 96% removal that seems to be what I expected :)

If your going to store it use a heater to increase the temperature in the container before you use it!
Or mix with luke warm tapwater!

That's the plan to mix with warm tap water when needed at desired temp.

May not be for this thread topic as WC related - but as I plan to 50/50 mix I will not need to remineralize?
 

tam

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I expect that it's not a temperature issue. Ours is located at the front of our garage - normal metal up and over door and fed from the cold water entering the house. The output is 0-1 straight after new filter install, and gradually creeps up over time. It does run slower when cold and obviously don't let is freeze. It's an RO-DI - but even with the extra stage I don't think temp seems to have a big impact on quality. Did you flush it first and discard the inital production? I'd see what a new jug full produces before changing other variables.
 

MichaelJ

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@Luvlyjub Efficiency (i.e. Gallons per day) is a function of water pressure and temperature - the efficiency with respect to removal of solids (TDS) should remain largely unaffected though. These are the factors for the RO Buddy 100 GPD. With a new membrane it takes me about 2 hours to make 5 US Gallon which is fairly consistent with my water temperature and pressure (at this time of year ~18 C / ~50 PSI at the hookup). My TDS out of the RO with a new membrane is 2-3 ppm... Right now with a fairly old membrane it is about 12 ppm.

So unless your water is very cold its not worth bothering about - pressure might be a bigger concern actually.

ROPSIT.jpg



As for remineralization, I would aim at using as much tap water as possible. I can't remember all your tank details, but I believe your setting up a scarcely planted Malawi tank, so water hardness won't really be a problem (Malawi's like harder water). So if you just want to shave off say 125 ppm for the sake of the Twinstar (?) you can use 75% of your 500 ppm Tap water and mix that with 25% RO water...

Also, when I do my 40% WC the WC water has usually reached a temp around 20-21 C, so when I drop it into the 24 C tanks I only get a gradual temperature drop of 1.5C at most ... The fish probably think its rain season :)

Cheers,
Michael
 
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Luvlyjub

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Did you flush it first and discard the inital production?
I had done and ran for 3 hours before test. It was interesting that I immediately had a lower TDS by increasing temp?

So unless your water is very cold its not worth bothering about - pressure might be a bigger concern actually.
Thanks Michael. That does make sense but my results seemed to suggest higher temp improved the recovery but I guess it was still running in the new membrane.

This water is for my nano tank 50/50 and Malawi tank (now moderately planted) is tap water only with good hardness and ready for fish in a couple weeks provided epiphytes don't melt this time!
 

Wookii

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As Darrel says, you only need a little tap water for your Nano tank if you are intending on keeping it as a soft water set-up (the only caveat to that being if you are keeping shrimp in there you'll ned more GH) - there is no point going through the effort of generating RO water just to add 250ppm TDS back in again.

As for the Malawi tank, I'm no expert on those, but I would have thought your tap water as-is, would have been fine given they require high KH/GH parameters.
 

dw1305

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Hi all,
It was interesting that I immediately had a lower TDS by increasing temp?
I assume that is to do with increased efficiency of the RO unit, electrical conductivity should increase with increasing temperature if everything else remains the same.

cheers Darrel
 

Luvlyjub

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he only caveat to that being if you are keeping shrimp in there you'll ned more GH
That was then plan to achieve a lower TDS and maintain a level of GH - so 50/50 seemed best option rather than full RO and remineralizing?

And yes Malawi is good old hard water from the tap - although I noticed the KH dropped over a period as tap is normally 7/8 and measured 5.5 before water change?
 

Wookii

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That was then plan to achieve a lower TDS and maintain a level of GH - so 50/50 seemed best option rather than full RO and remineralizing?

You don't need to necessarily use reminaraliser - but you don't need to mix 50/50 either. As I say, if you have no shrimp, 90% RO : 10% tap would be fine.
 

MichaelJ

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Thanks Michael. That does make sense but my results seemed to suggest higher temp improved the recovery but I guess it was still running in the new membrane.
That is interesting... Higher flow rate due to the increased viscosity of the water makes sense, but perhaps also a lower rejection rate (insignificant, but higher TDS) at the higher temperature - how much was the TDS difference and temperature difference in your setup?
 

Luvlyjub

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how much was the TDS difference and temperature difference in your setup?
My rejection rate was slightly better as initially it seemed to be 60/40 and with higher temp nearly 50/50.

I did not exactly measure the temp - I know exit water was 18deg before I turned it up. It seems the restricted flow to RO unit reduces my hot from mixer tap as at my normal mid setting it is 24deg pending conditions. Anyway I guess I tweaked it to around 24deg and achieved a reduction in TDS from 35 to 19.

Was going to run the test again with more accurate measurements and flushing to see if it was just because the membrane was new and running in.
 

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