Another Way of Emptying RV Holding Tanks

Disclaimer: this is a post about dealing with sewage. Read at your own risk!

This is one of those posts I really hesitated to write. I hadn’t found anybody else who deals with their holding tanks this way. Then I realised that just because no one else has done it doesn’t mean it can’t be done! So, I did it, and it worked, and it saved me a huge amount of time, hassle, and money, and I’m going to share it with you today.

I’m parked for about six months with no sewer hookup. Even if I had a macerator system to pump into a toilet ($$$) I don’t have a toilet to pump into. So, I planned on pulling out every six weeks or so to dump. The problem is that the dump is 20km away round trip and getting in and out of this spot is quite a bit of sport!

I decided after that one trip that pulling out was no longer an option. That left toting waste. I don’t have a blue boy and there’s another reason I’m hesitant to go that route: not being able to control the flow of the waste out of the tank. ‘Nudging’ a holding tank valve just doesn’t work, at least not with mine.

The main piece of the puzzle, then, was to figure out how to control the flow of waste out of the tank while minimizing the potential for making a mess.

The solution was quite obvious: empty the the tank from above, right in the bathroom.

The house that I owned really taught me to think outside the box. I remember one night when I had to empty the toilet to be able to remove it so that I could get a mechanical auger into the drain (fun times). That night, through a combination of trial, error, and conversations with my dad, I accidentally ‘invented’ the siphon. And that’s what I decided to do with my current holding tank situation.

Now, I have to say that since I went to dump I haven’t been putting paper in the tank so that I could prolong the tank getting too full. So I was dealing with a fairly liquid sludge, for which the siphon would work just fine.

These are the tools I gathered:

-newspaper for protecting the floors;

-disposable gloves;

-a large (6 gallon) bucket with a screw on lid;

-a piece of hose long enough to hit both the bottom of the tank and that of the bucket;

-paper towels;

-a garbage bag;

-a disinfectant;

-a wet/dry shop vac

First, I turned off the water pump, then I put newspaper down in both the dressing room and the toilet room to contain spills (unnecessary) and put the bucket into a garbage bag in case it leaked (unnecessary).  I then inserted the piece of hose into the tank, leaving enough out for it to rest on the bottom of the bucket.

A siphon is quite easy to make. The trick is that the liquid levels in the recipient container have to be lower than those in the donor container. So the ideal thing would have actually been to have the bucket outside, below the rig, and the hose snaked out the door, but I wanted to be able to keep my eye on the whole operation. So, I decided to siphon as much as I could and see where I got.

The other thing a siphon needs is a primer. In some cases, sucking on the hose would work, but not in this one! I used my wet/dry shop vac to create the necessary suction.

My set up worked perfectly and I was pleased to be able to fill up just a bit more than three quarters of the bucket before my siphon stopped working. The tank hadn’t been full to overflowing to start, so that freed up plenty of space. I made a note of how full the tank was when I siphoned it so that I’ll know when to repeat the exercise.

I screwed the lid on tight, brought the bucket outside for disposal at the dump station on the way to work tomorrow, cleaned the the shop vac, and then cleaned the bathroom and dressing room thoroughly for good measure. Done in about ten minutes with no mess.

Now, I can’t wait to hear from all the horrified people who will tell me that I shouldn’t have done that! 😀

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  • Hey, whatever works! 50 years ago my Dad used the bucket method of dumping the tank in our RV. He dumped it in the toilet in the house and though smelly for a few minutes it worked just fine. Probably wasn’t any different to him than his being a farm kid with no indoor plumbing.

  • I tried the bucket method in Campbell River, but found that there was too much risk of making a mess since it’s so hard to control the flow.

  • I had an idea.

    How about one of these with a shut off on the end of a very short hose…

    attached to one of these…

  • That is a great idea in theory, but, you still have to deal with a lot of pressure that shoots ‘stuff’ off in every direction. I have all the parts you mention, but I still think that’d be messier than my method.

  • “The problem is that the dump is 20km away round trip and getting in and out of this spot is quite a bit of sport!”

    The 20Km round trip certainly isn’t the deal breaker considering the fact that you only emptied about 4 gallons from the tank. The getting in and out would have to be a REALLY ‘bit of sport’ for me to go through this process to empty 4 gallons.

    “The trick is that the liquid levels in the recipient container have to be lower than those in the donor container.”

    I don’t see me doing this without a LONG siphon hose out the door. Where did you put the bucket to get it lower than your tank?

  • Ed, I didn’t completely empty the tank yesterday. If I had gone through the trouble of pulling out I would have, but I just gave myself some room to manoeuvre so I don’t have to pull out until the end of October.

    That was the cool thing about my siphon, it worked even though the bucket was just on the floor in the toilet room! It shouldn’t have worked, not as far as I understand how siphons work, but it did! Perhaps the trick was the amount of suction caused by the shop vac.

    I did the math on how much a 20KM costs, btw. I average 600km on a 200L tank. So that means that to drive 20KM I use up 7L of gas. So that’s $9 in fuel alone (at $1.30 per L) , not to mention all the time it takes to pack up, move out, do the deed, and get set up again (4 hours). $9 isn’t too bad for one time, but I would have had to do that at least 5 times this summer. I have other things I’d rather spend $50 and 20 hours on.

  • We already knew you were creative; this is just more evidence of that. Way to go, Rae!

  • Linda, that’s more like it! 😀 Thanks.

  • Fortunately, you don’t have our setup. Our shower drains into black. I think this was the “wise design” of the manufacturer to avoid the*black cone of death*. Needless to say, our valve gets pulled fairly frequently, but at least we have full hookups 😉

  • I would love your setup if I could switch it on and off! It’s so wasteful to have to use fresh water to flush!

  • Now that would be a great system!!

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