Dumping Tanks in 2014 Interstate

[weirdstuff]

Not sure if we did our first tank dump correctly or effectively.

Did our first tank dump on Sunday. Followed the directions on the little door flap.

We have the macerator, and the hose is pretty small. It's mostly clear, so you can see through it. When we dumped the black tank, we let the pump run until nothing more seemed to be coming out. Then closed black tank. Opened gray tank and turned pump on, and followed same procedure.

Checked tank levels. Both tanks showed as Empty.

Hooked up hose to flush black tank. I thought we were supposed to then fill black tank,and when it showed as full, then open it to dump it. But, directions on door flap seemed to say to turn hose on while leaving black tank valve open. We followed the directions.

When complete, we put 1-2 gallons of water + chemicals into the toilet.

Then, I checked tank levels. Black tank shows as 1/3 full (15 gallon tank) and no way did we put 5 gallons in to start it up. Grey water indicator shows as 1/3 full. HUH? It's a 30 gallon tank, that we thought we just dumped.

These levels don't seem right. Any idea on what we could have done wrong, etc..?

I know you're not supposed to run the pump on the grey water dump completely dry, so as soon as the indicator light dropped below 1/3 full, husband turned off pump.

[73shark]

You can pump both tanks dry but you just need to shut the pump off as soon as the tank is empty. Just don't run the pump long after the tank is empty and you'll be OK.

[Protagonist]

Main thing you seem to be missing is this:

There is no gauge inside the tank. Tank level is determined by transducers stuck to the outside of the tank. There are four transducers per tank, at the empty, one-third, two-thirds, and full positions.

So, when your tank is reading empty, that just means it's less than one-third full. When it reads one-third full, that means it's somewhere between one-third and two-thirds. And so on. So it's possible to go from showing empty to showing one-third full by just adding a couple of gallons, if it was just below one-third and you added enough to bring it just over one-third.

The empty and full indicators don't actually indicate that the tank is empty or full, just that they're close. Because of the shape of the transducer, and the shape of the tank, the empty transducer is slightly above empty, and the full transducer is slightly below full.

When you flush the black tank, you attach a hose to the exterior flush fitting, and put water in as it's being pumped out, stopping when the discharge is clear and odor-free. Then shut off the water, and leave the pump running until it runs dry. Because it's a diaphram pump (like a bellows), it can be run dry, briefly, before the motor begins to overheat.

If you flush the black tank until the discharge is clear, you don't really need to add chemicals until you're ready to use it again. I fill the toilet bowl completely full, drop in an enzyme packet, and once the packet dissolves, I flush the toilet. This when I first get to the campground. Then I'm good until I have to dump the tank.

[weirdstuff]

Thanks Protagonist. That makes complete sense. And it does look like we did the tank flush properly too, it just seemed contrary to my previous understanding of how to do it.

One more thing....It seemed that, when we dumped each tank, that the discharge was coming out the hose a little at a time. I had expected it to be a continuous flow.

I've since read that we should unravel the full length of the hose when we dump, even if we're closer to the dump station. This time, we were really close to the outlet, and just unravelled enough hose to reach the hole. Maybe that didn't allow the discharge to flow smoothly??

[jennian]

Is the exterior flush fitting the fill for the freshwater tank?
Do you need to flush on every discharge ?

[weirdstuff]

Originally Posted by jennian

Is the exterior flush fitting the fill for the freshwater tank?
Do you need to flush on every discharge ?

No, it's a separate fitting, and it's labeled as FLUSH, or FLUSH VALVE, or something like that.

My understanding is that it's ideal to flush on every discharge if possible. But, what do I know? That was our first ever tank dump!

[Protagonist]

Originally Posted by weirdstuff

I've since read that we should unravel the full length of the hose when we dump, even if we're closer to the dump station. This time, we were really close to the outlet, and just unravelled enough hose to reach the hole. Maybe that didn't allow the discharge to flow smoothly??

Diaphragm pumps pump in spurts. It's normal.

But it's still best to unreel all of the hose every time. The hose reel is vertical. If you leave most of the hose on the reel, each loop has a low point, and that's a lot of water left in the hose. By unreeling the entire hose, you ensure that there are no low points in the hose for water to collect.

Flushing on every black tank dump is good; it ensures a minimum of solids buildup. On a late-model Interstate, the flush fitting is in the same compartment as the discharge hose, and probably isn't labeled. But being in that compartment, it's hard to confuse it with anything else.

[MeandMB]

Great question and again great answers by those in the know. Never surprised by the in depth response to all questions that seem quite difficult to us new guys. 10-4 to all, with special attention to Protoganist.

Joe

[weirdstuff]

Yea, that. So grateful for the time you all spend in helping the rest of us learn!

[russ240]

I flush the black tank every third or fourth dump myself. When I flush it, I always flush it immediately after dumping the black and before I dump the grey tank. I always want to finish my dump sequence with the grey tank so the last thing that runs through the dump hose is soapy water not .... um how shall I say this delicately ... toilet water. When I flush I let it fill the tank with the pump off (either by watching the lights increment upwards or looking down through the toilet with a flash light while holding the pedal down) then I turn on the pump. I find the pump empties faster than the hose fills so the pump eventually catches up and that's when I'm done. Well, sometimes I actually do it again once or twice before I call it quits, but I'm a little OCD.

When dumping each tank I let the pump run until I hear it change pitch when it hits empty, then I let it run another 15-30 seconds. I find that the flow is quite steady when there is plenty of supply to the pump but when the tank runs dry and the pitch changes that is when the flow starts to spurt. In my experience it never stops spurting no matter how long you let it run, you just cant get it all out of the hose. If you found the flow to be spurting right from the get go I suspect you may have been dumping so prematurely that you never even got a full flow out of the pump. If you never heard the pitch change as the pump started running with no real load then I would be pretty certain that is what happened.

My two cents.

[weirdstuff]

Russ240, Thanks for sharing how you do it. Appreciate all input here. I wonder if the macerator, etc., system in your 2012 is the same as in my 2014. Want to know if we're dealing with the same system.

We waited until the black tank Full indicator light came on, before we dumped. So def not dumped prematurely.

[Protagonist]

Originally Posted by Protagonist

Diaphragm pumps pump in spurts. It's normal.

Should have said it pulses. Doesn't become a spurt until you start sucking air (when the 3" line feeding the pump isn't full all the way to the top).

Centrifugal pumps and turbine pumps have a smooth flow because they spin and are taking in fluids at the same rate they expel them, but a diaphragm pump has a separate inlet stroke and outlet stroke. Macerator pumps start to slow down when they are grinding up the solids. The grinder runs off the same motor as the pump itself, so the more the grinder has to work, the less horsepower is available to the diaphragm.

I think the macerator pump is the same for all Interstates that have one, a Flojet 18550. Maximum flow rate 13 gallons per minute (no solids), average flow rate 10 gallons per minute. So to empty an Interstate's black tank should take less than a minute and a half, and the gray tank should take less than 3 minutes.

[gmillerok1]

While the water pump for the fresh water is a bellows design, the Flojet Macerator pump is not. It uses an impeller. The instructions clearly warn not to run it dry or the pump could be damaged.

Gerald

Originally Posted by Protagonist

...Because it's a diaphram pump (like a bellows), it can be run dry, briefly, before the motor begins to overheat.

[Protagonist]

Originally Posted by gmillerok1

While the water pump for the fresh water is a bellows design, the Flojet Macerator pump is not. It uses an impeller. The instructions clearly warn not to run it dry or the pump could be damaged.

I stand corrected. Thank you!