Evaporation rate

Shawn_epicurious · Jun 12, 2020

I don’t know if this is actually a chemistry question or not. My apologies if I asked this in the wrong place.

I have been trying to get my hands on a flow meter for my RODI. I’ve recently discovered there is way more water running through that thing than I thought. ....new filters/canisters are on the way...

I have a 200 gallon tank, LED lighting and an open top. I don’t have a lot of ripple action on the surface of my water when viewed from underneath. My tank stays berween 77.5f and 78.5f religiously.

How do I calacluate... or you know.... just guess what my evaporation rate is?

Rjmul · Jun 12, 2020

I read this more than three times. Is your RO hooked up to your ato container? If so cut it off and see how long the container lasts ?

Rick.45cal · Jun 12, 2020

Shawn_epicurious said:
I don’t know if this is actually a chemistry question or not. My apologies if I asked this in the wrong place.

I have been trying to get my hands on a flow meter for my RODI. I’ve recently discovered there is way more water running through that thing than I thought. ....new filters/canisters are on the way...

I have a 200 gallon tank, LED lighting and an open top. I don’t have a lot of ripple action on the surface of my water when viewed from underneath. My tank stays berween 77.5f and 78.5f religiously.

How do I calacluate... or you know.... just guess what my evaporation rate is?

Are you allowing your RO/DI unit itself to top off your sump via a float valve, and not using a separate ATO? If you are, that’s a bad idea (In my opinion) for several reasons. 1. Shortened life of your DI resin due to TDS “creep“ everytime the unit cycles on and off. 2. Possible flooding should your float valve fail, and also lowering your tank salinity in the process.

If you run an ATO unit via a separate reservoir you can easily calculate the daily evaporation rate via the change in the volume of the ATO reservoir. (I personally wouldn’t allow my RO/DI to top off the ATO reservoir either).

Shawn_epicurious · Jun 12, 2020

Rjmul said:
I read this more than three times. Is your RO hooked up to your ato container? If so cut it off and see how long the container lasts ?

Hadn't thought of that! I can do that : )

Mine is directly plumbed to the sump, no reservoir

Rick.45cal · Jun 12, 2020

Shawn_epicurious said:
Hadn't thought of that! I can do that : )

Mine is directly plumbed to the sump, no reservoir

This is an accident waiting to happen in my experience

Shawn_epicurious · Jun 12, 2020

Rick.45cal said:
Are you allowing your RO/DI unit itself to top off your sump via a float valve, and not using a separate ATO? If you are, that’s a bad idea (In my opinion) for several reasons. 1. Shortened life of your DI resin due to TDS “creep“ everytime the unit cycles on and off. 2. Possible flooding should your float valve fail, and also lowering your tank salinity in the process.

If you run an ATO unit via a separate reservoir you can easily calculate the daily evaporation rate via the change in the volume of the ATO reservoir. (I personally wouldn’t allow my RO/DI to top off the ATO reservoir either).

Yes, that is the way mine is set up... no reservoir... yes, float valve in sump. To be honest (necessity is the mother of invention right??) I have put off learning about my RODI and now it is messing me up a bit, so yeah, I am starting to catch up on how this thing is suppose to work.

Here is my confusion... either set up will still use the same amount of water... it still needs to top off.... right? I am not sure I understand the advantage of what you are suggesting. A flow meter solves it? right?

Honestly? I am just really surprised at how much it is topping off.... maybe that’s where I am missing the moral here. It’s way more Usage than I thought it would be : )

Rjmul · Jun 12, 2020

Shawn_epicurious said:
Hadn't thought of that! I can do that : )

Mine is directly plumbed to the sump, no reservoir

I wouldn't do that. Get yourself a nice little aqueon tank as a resavoir.

A. That's one less way to flood your house
B. You'll know how much evap you have.
C. You can dose SOME stuff through an ATO. When I need to use lanthinum chloride, that's how I do it.

Shawn_epicurious · Jun 12, 2020

Rjmul said:
I wouldn't do that. Get yourself a nice little aqueon tank as a resavoir.

A. That's one less way to flood your house
B. You'll know how much evap you have.
C. You can dose SOME stuff through an ATO. When I need to use lanthinum chloride, that's how I do it.

......curves in my path... you just presented me with a good one : ) ......already googling ot : J

Rick.45cal · Jun 13, 2020

Shawn_epicurious said:
Yes, that is the way mine is set up... no reservoir... yes, float valve in sump. To be honest (necessity is the mother of invention right??) I have put off learning about my RODI and now it is messing me up a bit, so yeah, I am starting to catch up on how this thing is suppose to work.

Here is my confusion... either set up will still use the same amount of water... it still needs to top off.... right? I am not sure I understand the advantage of what you are suggesting. A flow meter solves it? right?

Honestly? I am just really surprised at how much it is topping off.... maybe that’s where I am missing the moral here. It’s way more Usage than I thought it would be : )

An ATO and a reservoir are important because in the case of a failure (of the float valve, or the solenoid turning on and off the RO/DI) you are limited in the volume of fresh water that can be accidentally added. Should your current setup fail, then it may be a large flood depending on when it happens (while you are asleep or away from the house) before you realize it.

The added benefit of running your RO/DI into a seperate storage reservoir (not associated with the ATO‘s reservoir). Is that you can flush the initial water from the RO membrane down the drain before it goes to the DI resin when you start the unit up to fill the reservoir. TDS creep is excess dissolved solids that have made it passed your membrane while it was sitting idle, these are absorbed by the DI resin but if you bypass the DI resin in the beginning until the TDS drops to it’s operating level you will save some life in your DI resin and it will have to be replaced less frequently. It only takes a couple of minutes

You can add a float valve to your DI water storage tank so you don’t have to babysit it and not worry about having an overflow because you forgot when you were making water (happens to all of us at some point). But by physically operating the unit yourself when you need to make water. You are significantly lessening the risk of having a big flood.

So now to make life easy, you can plumb your DI water reservoir with a pump to your ATO reservoir with ball valves, and then when your ATO reservoir needs to be filled up, you just turn on a pump and open a valve and fill the ATO reservoir. That way you aren’t carrying around buckets of water, and you can safely make larger quantities of fresh water and store them without the risk of flooding everything with an accident. (This is how mine is set up).

Shawn_epicurious · Jun 13, 2020

Shawn_epicurious said:
......curves in my path... you just presented me with a good one : ) ......already googling ot : J

Wait... I am having trouble letting this one go : )

Currently, I have a 2 float system in my sump... one that allows water in and another one about an inch higher, that is a shut off. If I add a reservoir, I’ll have a 2 float system. In my sump, I have room for... An extra 30 gallons... easy. A reservoir? How much extra room? A gallon?

I get the added measurement ability....I get having an additional means of dosing... I do not get the “extra safety piece?”

Rick.45cal · Jun 13, 2020

It’s ok to have it the way you have it, you’ve got some redundancy built in. In my experience having a limiting factor like a 10 gallon ATO reservoir means should everything fail then at most my tank can only get 10 gallons of fresh water dosed into it. Which in itself might not be great because of the drop in salinity, but it would be minor compared to having a direct water line to your tank running non stop. You might have room for 30 gallons of water, but adding 30 gallons of freshwater to your aquarium probably isn’t going to make things happy, and will likely result in some losses.

I’m just putting forth a worst case scenario because in my experience, eventually everything in this hobby fails, and things tend to fall like dominoes when it happens. Float valves are great pieces of equipment and work most of the time, but I have known more than a few aquarists in my days who have had major floods having their tank hooked up to the RO/DI.

ATO systems aren’t flawless, and accidents/ failures happen. Having a limited quantity of water that physically can be added to the tank is really the only true fail safe, in my opinion.

Shawn_epicurious · Jun 13, 2020

Rick.45cal said:
It’s ok to have it the way you have it, you’ve got some redundancy built in. In my experience having a limiting factor like a 10 gallon ATO reservoir means should everything fail then at most my tank can only get 10 gallons of fresh water dosed into it. Which in itself might not be great because of the drop in salinity, but it would be minor compared to having a direct water line to your tank running non stop. You might have room for 30 gallons of water, but adding 30 gallons of freshwater to your aquarium probably isn’t going to make things happy, and will likely result in some losses.

I’m just putting forth a worst case scenario because in my experience, eventually everything in this hobby fails, and things tend to fall like dominoes when it happens. Float valves are great pieces of equipment and work most of the time, but I have known more than a few aquarists in my days who have had major floods having their tank hooked up to the RO/DI.

ATO systems aren’t flawless, and accidents/ failures happen. Having a limited quantity of water that physically can be added to the tank is really the only true fail safe, in my opinion.

Nice write up... okay, I get it now. : ) I was not considering the change in salinity.

jccaclimber · Jun 14, 2020

The increased safety for several reasons:
1. No salinity shift if the RO unit flows unrestricted.
2. Unless you have laminate wood flooring, or other flooring/trim made out of compressed wood, the ramifications of a 0TDS flood are much lower than the ramifications of a salt water flood. RO/DI water dries up and leaves nothing behind. Salt water leaves all that salt soaked in to things, which also means there’s a bit more moisture retained by the residual salt.
3. The assumption is that your RO unit is manually shut off most of the time. For example, my last big tank had a 50 gallon top off container, and it lasted 1-2 weeks. I actually filled it with a hose from my RO tank in the garage, but pretend for a bit that I was filling it directly from my RO unit. I would see it getting low, turn the RO unit on in the morning, let it fill up 40 gallons to the top, and the float valve would stop it. That evening I would see that it was full, and manually shut off the water source to the unit. For a half day I have the same risk level as you, but for the next 6 to 13 days until I turn it on again I have a very low risk because the water is shut off at the tap.
4. Most ATO units have a safety built in so that they shut off and alarm if they run for too long. This prevents a large salinity swing, assuming the RO unit refilling the ATO reservoir could keep up.
5. Say you have a leak in your sump. I’ve had this in the form of an improperly secured drain line. If the ATO keeps running your salinity keeps dropping and the flood continues, plus your return pump starves. If the ATO shuts off, or runs out of water your return pump still starves, but your display doesn’t significantly change salinity, your sump may not either, and the flood has a limited magnitude.

This does come at the increased risk of having an ATO pump fail. You can easily make that a redundant system if that is a concern.

As an added benefit, you can now dose through your ATO chamber. Want to boost your salinity gradually over a week? Put a week’s worth of water in your ATO and throw the salt in there. Magnesium or another element? Same thing. After a couple normal drain/refill cycles it’s close enough to clean that you can dose something else.

Randy Holmes-Farley · Jun 14, 2020

Back to the original question, most tanks evaporate on the order of 1-4% of the water volume daily.

X-37B · Jun 14, 2020

I use a 10 gallon ato container.
I have to fill it twice a week.
Evaporation rate is about 2 gallons a day.
A small ato will also keep you intouch with your tank and is easy to monitor.