Originally Posted by SmokelessJoe
Does this mean that the Interstate has only ONE waste tank? If so, what a shame. And poor design too.
No. Late-model Interstates have one 26-gallon gray tank and one 26-gallon black tank. Both feed to the macerator through separate valves. Since on-board fresh water is 26 gallons in the fresh tank plus 6 gallons in the water heater, there's little danger of overflowing either waste tank while boondocking, if you dump the waste tanks every time you fill the fresh tank.
Letting the gray tank run free is not a great option even with a macerator pump that has a graywater bypass. Since the Interstate's 1" discharge hose is permanently attached, the only way the hose ever
gets rinsed out is by pumping out the soapy gray water after
the black water, or by using the heck out of the black tank flush fitting until the water comes out clear.
I've been using my Interstate for a year and a half, sometimes with full hookups, sometimes at campgrounds with dump stations. I'm pretty frugal about water usage, but when I have full hookups, I make a point of setting up a schedule for dumping the tanks. For me, once every four days is plenty often, since I've been known to stretch my water supply out to seven days by judicious use of sponge baths that are even more water-saving than a Navy shower (but then again, I am a solo camper).
Pumping out the tanks isn't terribly onerous. The macerator will pump out about 8 gallons per minute, so it only takes three minutes per tank to get them emptied. The black tank does take slightly longer if there are a lot of solids to chew up.
Easy way to figure out a schedule for how often to dump your tanks, go to a campground with full hookups. Then, fill the fresh tank, and don't connect the fresh water hose. Then use water from your fresh tank until you run out. That tells you how long it will take to use 26~32 gallons of water. That's also about how often you should dump the tanks to ensure your peace of mind.
Once you've used the fresh tank for one complete fill/empty cycle, hook up to the municipal water supply like normal people, and remember to dump the tanks whenever you've used 26~32 gallons of water.
One other point to remember, even though you can use the macerator pump without unreeling all
of your hose, go ahead and unreel it all anyway. Pumping out while the hose is partially spooled up traps water in the hose that would otherwise drain out.
I've never had the hose bind tight enough to split it. The fuse for the take-up reel should
have blown before things got that bad. I've blown fuses three times on my take-up reel, but two of those times were on my very first trip, before figuring out how to reel the hose in more slowly— one hand on the hose to guide it, one hand on the switch to stop the reel if the hose doesn't spool up properly on the reel. That gives me the opportunity to pull the hose back out partway and try again before it binds. The other time I blew a hose reel fuse, it was in a howling thunderstorm but I had to get back home so I could report to work the next day, and I got in a hurry and forgot my own technique. Lot of good that
did, because I had to change the fuse and go back
out into the storm to finish reeling in the hose.
Airstream could have put in a better hose reel with a built-in guide roller. They could have put a second set of tank level gauges outside by the macerator pump controls so you don't have to go back inside to make sure you've pumped the tanks dry. They could have put in a screw fitting so that you could unscrew the hose and remove or replace it more easily. They could have made the hose reel compartment bigger so the nozzle fits inside more easily. But they didn't. I don't mind, much. It's what I'm accustomed to, now.
And, at almost every campground I go to, I see people with slinkies who tell me they wish they had a macerator pump instead, because the discharge hose is so clean and easy to handle compared to a slinky.