PDA

View Full Version : auto waterchange question


Mrs. Music
09/12/2017, 08:25 PM
Could a batch of water with a pump on a timer set to run water for a few minutes every day and a bulkhead drain set high in the sump work as an auto water change system? does that make sense?

der_wille_zur_macht
09/12/2017, 08:55 PM
It could, but it would make me nervous. First, how are you accounting for topoff? Do you know for sure that your topoff approach won't interfere with that design? For instance, let's assume you're using a standard float switch based ATO. You'd need to set the switch at least a little bit below the water change drain bulkhead, otherwise it would never shut off. Now, every time you do a water change, you're essentially going to be adding more water than you're taking out, since you have to add some to get to the point where it starts draining. You could account for this by using a slightly lower salinity in the water change system.

Second, and maybe just as obvious, are you sure you can protect the drain? NOTHING will go down it? Snails can't climb into it, or block it?

The "best" water change systems for marine tanks are the systems where both the input and output water are metered, so you know they match. In a FW tank this isn't a big deal. I did exactly what you're describing in my 360g when it was running as a FW tank, I let water run from my RO/DI unit right in to the tank and the overflow went out through a hose into the garden. Never had an issue but I only ran it when I was home and monitoring the tank, and since it was FW I didn't need to worry about evap/topoff and messing up the salinity.

There's also the point that any such system will be inherently wasteful, in that some of the water going out the drain will be "new" water, although you can minimize that with good design.

Mrs. Music
09/13/2017, 01:20 PM
thank you for the thorough answer. My thought was to put the new water line at the far left of my 75 gallon sump into the skimmer section and place the bulk head drain/ at the far right/ last section of my sump. Placing the bulk head drain above normal water level line with it draining into my sink.

Sharpimage
09/14/2017, 01:25 PM
It is a bad idea. It will mess with your ato. Say it kicks on right before your ato starts. It will add, just say 2 gallons, of fresh salt water. your ato will not kick in, the drain will remain dry. and you just replaced your ro with salt water. Your salt level will creep up.

Mrs. Music
09/14/2017, 06:31 PM
It is a bad idea. It will mess with your ato. Say it kicks on right before your ato starts. It will add, just say 2 gallons, of fresh salt water. your ato will not kick in, the drain will remain dry. and you just replaced your ro with salt water. Your salt level will creep up.

Ok, so that is a consideration.

sailfish
09/15/2017, 02:44 PM
Look at the litermeter, they have a water exchange module that can be implemented. I have used their stuff for Auto top off for 8 years or more. It is very precise.

Moto443
09/16/2017, 08:40 PM
You would also want to consider what would happen in the event of a power outage, or if you have to shut the return pump off. Your sump would fill with water from the DT, which would drain. When power is returned, your ATO would replace that with freshwater.

Mrs. Music
09/17/2017, 07:13 AM
Thank you for all of your input. As there are way too many points of failure for this idea, I am gonna let it go.