Understanding filling and draining of balast

[HaulnSS]

I have an 03 Moomba Mobius with a single ballast "tank" under the rear seat. This is a white plastic tank that the seat itself sits on. The ballast fills fine, but I had to manually drain it.

Here is the part I don't understand, I have the Rule HighFlow livewell pump that pulls the water from the lake to fill the ballast, after that, is the solenoid. I don't understand the purpose of this, as I only have one tank, the hose continues through a Rule Aerator pump and into the bottom of the ballast. Is this typical? It just doesn't make sense to me, how does this drain the ballast? The aerator pump kicks on, but doesn't drain the tank. I disconnected a quick disconnect after the solenoid to drain the ballast into the hull.

Are both pumps (fill pump and empty pump) suppose to be on the same hose? Where is the ballast suppose to drain in this scenario?

Any help would be appreciated!

[jasonwm]

I have not seen a Mobius with that specific system installed, but your description is very detailed and sounds accurate.

Moomba uses the same basic setup, regardless of how many bags or tanks are installed in the boat. In your system, the solenoid is preventing the tank from draining when the boat is running, which can happen due to the venturi affect caused by the water flowing over the thru-hull intake. In boats with more than one tank/bag, the solenoids are used to route the water from the one fill pump to the various locations depending on which switch on the dash was turned on.

It's important to understand that the pumps you have are aerator style pumps, which DO NOT block the flow of water when they are turned off. That's why it is possible for the fill and drain pumps to essentially be connected to the same hose.

Here's the basics of how your system functions:

Filling:
Turning on the fill switch engages the Rule 2000GPH fill pump and opens the solenoid opens allowing water to be pumped into the tank through the drain pump.

Draining:
Tuning on the drain switch engages the drain pump connected directly to the tank and opens the solenoid allowing water to be pumped back out of the tank through the fill pump. I would imagine that draining will only be reasonably quick when the boat is stationary.

If your drain pump is working correctly I would check to make sure the solenoid is actually opening when the drain pump is turned on.

[HaulnSS]

I have not seen a Mobius with that specific system installed, but your description is very detailed and sounds accurate.

Moomba uses the same basic setup, regardless of how many bags or tanks are installed in the boat. In your system, the solenoid is preventing the tank from draining when the boat is running, which can happen due to the venturi affect caused by the water flowing over the thru-hull intake. In boats with more than one tank/bag, the solenoids are used to route the water from the one fill pump to the various locations depending on which switch on the dash was turned on.

It's important to understand that the pumps you have are aerator style pumps, which DO NOT block the flow of water when they are turned off. That's why it is possible for the fill and drain pumps to essentially be connected to the same hose.

Here's the basics of how your system functions:

Filling:
Turning on the fill switch engages the Rule 2000GPH fill pump and opens the solenoid opens allowing water to be pumped into the tank through the drain pump.

Draining:
Tuning on the drain switch engages the drain pump connected directly to the tank and opens the solenoid allowing water to be pumped back out of the tank through the fill pump. I would imagine that draining will only be reasonably quick when the boat is stationary.

If your drain pump is working correctly I would check to make sure the solenoid is actually opening when the drain pump is turned on.

So it is suppose to drain back through the hull from where it fills. This just didn't seem right to me. I will hook it all back up and try out the solenoid as you suggested.
Thank you for your help!

[jasonwm]

Yep, it's one way to design a system that uses aerator pumps to reduce the number of components and the amount of man hours required for installation. It's typically not the best way to do it (it's not very flexible), but it will certainly work.

[lowdrag]

Hmmmmmm.....I don't know about your setup, but I specifically remember on my '03 LS with the hard tank that the drain pump would pump the water out of the hull fitting and not back out the fill port.

[moombadaze]

Hauln, is there a empty port on the side of the boat? like the bilge pump has.

[HaulnSS]

Hauln, is there a empty port on the side of the boat? like the bilge pump has.

The top of the tank has two hoses, that go to each side of the boat. They are just there for overflow I guess.

[HaulnSS]

Yep, it's one way to design a system that uses aerator pumps to reduce the number of components and the amount of man hours required for installation. It's typically not the best way to do it (it's not very flexible), but it will certainly work.


Jason, While I have this all apart, is there a better way for me to drain the tank? I was thinking about running the filler pump to the top of the tank and run the drain pump out the side of boat. Is the drain pump strong enough to handle the change?

Thanks!

[jasonwm]

Yes, that is exactly what I would do! You'll be able to fill and drain whether you're sitting still or running at speed, and you won't have nearly as much internal restriction.

[HaulnSS]

Yes, that is exactly what I would do! You'll be able to fill and drain whether you're sitting still or running at speed, and you won't have nearly as much internal restriction.

Excellent, That is what I will do! I greatly appreciate the help!

[jasonwm]

No problem, let us know how it turns out.