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Evaporation and RODI Filters

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Evening all,

I'm looking into RODI Filters and was hoping you guys could give me some advice based on your experience?

First off, if I'm going to be doing a 10% water change on a 350L tank then I'll need 35L of RO water per week. Thats easy enough to work out.

But on top of that, the ATO needs refilling but I'm not sure how much water evaporates per week. Can someone enlighten me on this?

Now this is the bit that gets me thinking. I won't have much space for water storage because my house wont have a garage but I have asked the wife if I can commandeer the space under the stairs for storing big fish stuff, to which she kindly agreed. She's a good 'un :) as a rough guess I would say I can comfortably keep 50L of RO water in there. The plan would be to get the RODI filter running on a weekend to prepare for the upcoming week. If I need, say about 50L per week, (about 13gallons?) then would a 50gpd filter be able to manage that in about (edit:) 6 hours? Give or take a bit. In this case, would there be any benefit to having a 75gpd or 100gpd filter other than it producing water faster?

Thanks in advance!
Rad91



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Last Edit: Dec 21, 2017 10:58:08 pm by Radiation91

Asco1104

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Reply #1

There’s no real calculation because the numbers are so variable. I would have a guess that you might use 20 litres a week but that is a guess.
You will use more on top up in the winter compared to the summer too.

A 50 gpd would make 9.4 litres a hour roughly, but this depends on water temperature going in, water pressure and condition of the membrane.
My advice would be to by as high a gpd unit as you can afford factoring in service costs.

Always nice to have your partner in your corner


Tim

Radiation91

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Reply #2

There’s no real calculation because the numbers are so variable. I would have a guess that you might use 20 litres a week but that is a guess.
You will use more on top up in the winter compared to the summer too.

A 50 gpd would make 9.4 litres a hour roughly, but this depends on water temperature going in, water pressure and condition of the membrane.
My advice would be to by as high a gpd unit as you can afford factoring in service costs.

Always nice to have your partner in your corner


Tim
Hi Tim. Thanks for the input! Having a rough idea of about 20litres per week is useful. That's something that I just can't estimate since I have no experience with it.

Can I ask why I would expect more evaporation in winter? I would have thought it would be lower in winter because it will be a cooler room temperature? I'm not arguing here btw. I'm genuinely interested :)

Cheers
Rad91

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ajm83

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Reply #3

My evaporation rate is between 0.5 and 3% per day. Closer to the top end of that at the moment.  Maybe because the heating is on more this time of year? Dunno. 

It's an uncovered tank & sump.  You can cut it back significantly with a cover.

I'm with Tim on the speed, get the fastest you can. 

I get about 10L/hr in summer with my 50GPD unit,  much less in winter.  My water pressure is good, expect lower rates if water pressure is under 60PSI (or factor in the cost of a booster pump).  ;)

Also, I don't have a garage either so I store my RODI in a water butt outside in the garden, plus a couple of emergency 25L containers stashed in the loft...
Last Edit: Dec 22, 2017 11:35:10 am by ajm83

Asco1104

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Reply #4

It’s because the air in the winter is drier and it’s made worse by heating being on, this allows more moisture to be drawn from your tank because there’s more space for it in the air.


Tim

Thanks:


Gav

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Reply #5

I'm around 2l of RO top off per day max which includes skimming rather wet and evaporation on a similar sized system .

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Reply #6

As said, it massively varies.  How dry is the air in your house?  How big is the surface area of the tank?  How much water movement is there, making that significantly larger?  Etc.  You're unlikely to find an RODI that won't keep up with your demand though.  It's more a question of how quickly you want to produce it.  Get 100L done in an hour and have it over with, or produce smaller amounts more often, or the larger amount over a few hours. 

I highly recommend calling Vyair www.vyair.com and asking them for advice for a marine tank.  Their customer service is excellent.

Radiation91

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Reply #7



I'm with Tim on the speed, get the fastest you can. 

I get about 10L/hr in summer with my 50GPD unit,  much less in winter.  My water pressure is good, expect lower rates if water pressure is under 60PSI (or factor in the cost of a booster pump).  ;)

Also, I don't have a garage either so I store my RODI in a water butt outside in the garden, plus a couple of emergency 25L containers stashed in the loft...

Good stuff... I won't know about the water pressure until next June so I will have to wait until then to see if i need a booster pump. Thanks for he info :)

Nice to meet someone else without a garage... and I never thought about the water butt idea. That could be a very useful!

It’s because the air in the winter is drier and it’s made worse by heating being on, this allows more moisture to be drawn from your tank because there’s more space for it in the air.

Ahhhhh that's clever. Nicely explained :)

I'm around 2l of RO top off per day max which includes skimming rather wet and evaporation on a similar sized system .

Thanks. I'll say about 20L as a rough estimate and take it from there :)

As said, it massively varies.  How dry is the air in your house?  How big is the surface area of the tank?  How much water movement is there, making that significantly larger?  Etc.  You're unlikely to find an RODI that won't keep up with your demand though.  It's more a question of how quickly you want to produce it.  Get 100L done in an hour and have it over with, or produce smaller amounts more often, or the larger amount over a few hours. 

I highly recommend calling Vyair www.vyair.com and asking them for advice for a marine tank.  Their customer service is excellent.

That's a good point. I suppose if I bought one at 50gpd then I have to put 8 hours aside per week to get it done. Let's face it, that's most of Saturday gone. If I get a faster one then I've got some leniency about what time of day I get the water done.

Thank you everyone! This has been helpful!

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ajm83

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Reply #8


Good stuff... I won't know about the water pressure until next June so I will have to wait until then to see if i need a booster pump. Thanks for he info :)

Nice to meet someone else without a garage... and I never thought about the water butt idea. That could be a very useful!

Ahhhhh that's clever. Nicely explained :)

Thanks. I'll say about 20L as a rough estimate and take it from there :)

That's a good point. I suppose if I bought one at 50gpd then I have to put 8 hours aside per week to get it done. Let's face it, that's most of Saturday gone. If I get a faster one then I've got some leniency about what time of day I get the water done.

Thank you everyone! This has been helpful!

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Don't have time to answer properly but you can get an auto shut-off with a float valve so you don't have to wait around

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Radiation91

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Reply #9

Don't have time to answer properly but you can get an auto shut-off with a float valve so you don't have to wait around

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Good point

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