Excessively complicated automatic water change setup for your amusement

[thermoJoe]

So, a few months back I finally setup a system for automatic water change using just one Masterflex pump with two pump heads (one to add new artificial sea water (ASW), the other to remove old aquarium water). I put in a needle valve on one of the lines so that I could then make sure both were delivering and removing the same volumes (about 1.5 gal/day). The problem I ran into in this setup was that as the feed drum with fresh ASW empties, the pressure head on the feed pump changes, which in turn changes the flow rate. Over a period of a month or so, the difference in flow rates resulted in either too much ASW being added, or too much tank water being removed, which caused a gradual increase or decrease in tank salinity accordingly. I got tired of also recalibrating the system with each new filling of the ASW reservoir, after all, one of the main reasons for AWC is to reduced tank maintenance time.

About a month or so ago I redid the system adding in two more masterflex pumps, but instead of relying on pump flow rate calibrations, I instead introduced two small 2 L reservoirs (see pic) with float switches connected to an Apex controller. Using the OSC apex command, the system now first fills each 2 L reservoir, one with the fresh ASW and the other with old tank water. In this case, the pumps don't need to be calibrated because the pumps are turned off once the float switch is triggered (there are redundant float switches that go off if the first fail). Once the 2 L reservoirs are filled, the pump with two pump heads turns on and empties the fixed volume reservoirs to the appropriate locations (down the drain or into the tank). Right now, three fill/empty cycles are run per day, with the Apex programmed somewhat similar to what you do with their auto food feeders.

So far, it's been working well with "exactly" 6 L of new ASW added and "exactly" 6 L of old tank water removed. But, ya, many points of failure now, but I'm OK with that, plus I get some joy out of this ridiculousness.

 

[BighohoReef]

Nothing that a little clean re-engineering won't solve How do you keep track of all the cords, cables and piping?

 

[Cell]

Just turn the lights off and back away slowly.

 

[thermoJoe]

lol, yup. They are labeled and color coded.

 

[Pistondog]

So, a few months back I finally setup a system for automatic water change using just one Masterflex pump with two pump heads (one to add new artificial sea water (ASW), the other to remove old aquarium water). I put in a needle valve on one of the lines so that I could then make sure both were delivering and removing the same volumes (about 1.5 gal/day). The problem I ran into in this setup was that as the feed drum with fresh ASW empties, the pressure head on the feed pump changes, which in turn changes the flow rate. Over a period of a month or so, the difference in flow rates resulted in either too much ASW being added, or too much tank water being removed, which caused a gradual increase or decrease in tank salinity accordingly. I got tired of also recalibrating the system with each new filling of the ASW reservoir, after all, one of the main reasons for AWC is to reduced tank maintenance time.

About a month or so ago I redid the system adding in two more masterflex pumps, but instead of relying on pump flow rate calibrations, I instead introduced two small 2 L reservoirs (see pic) with float switches connected to an Apex controller. Using the OSC apex command, the system now first fills each 2 L reservoir, one with the fresh ASW and the other with old tank water. In this case, the pumps don't need to be calibrated because the pumps are turned off once the float switch is triggered (there are redundant float switches that go off if the first fail). Once the 2 L reservoirs are filled, the pump with two pump heads turns on and empties the fixed volume reservoirs to the appropriate locations (down the drain or into the tank). Right now, three fill/empty cycles are run per day, with the Apex programmed somewhat similar to what you do with their auto food feeders.

So far, it's been working well with "exactly" 6 L of new ASW added and "exactly" 6 L of old tank water removed. But, ya, many points of failure now, but I'm OK with that, plus I get some joy out of this ridiculousness.

Is this a peristaltic pump?
Aren't they constant volume regardless of supply tank volume, within reason?
Were the supply tanks above or below the pumps?
Aren't most dosing pumps peristaltic, with reservoirs lower than pumps?
Why wouldn't this work in your case?

 

[thermoJoe]

Is this a peristaltic pump?
Aren't they constant volume regardless of supply tank volume, within reason?
Were the supply tanks above or below the pumps?
Aren't most dosing pumps peristaltic, with reservoirs lower than pumps?
Why wouldn't this work in your case?

Yes, they're peristaltic pumps, and quite good ones at that, but flow is still impacted some by changing pressure head. But you're right, I was quite surprise at just how different the two flows could be even though I used the exact same tubing and pump heads, and both were driven by the same pump, so had the exact same RPM. The addition of the needle valve did allow the flows to be equalized, but it made the system even more sensitive to changes in pressure head (and it could also get fouled easier).

Oh, to answer your other question, the supply tank and aquarium are on the same floor, but in a basement, so the waste flow must be pumped up ~6 ft to get to a drain, but the feed tank sits on the floor along with the sump. Overall, the difference in head between the two is at most ~10 ft.