I have a Mantis and sometimes I find the compost getting very wet. When that happens, I leave the door flap open allowing more air to get in. This helps in addition to turning it frequently.
I can make compost in a few weeks depending on if I have enough material - greens this time of year added to the stash of leaves from the fall. If I can completely fill the bin and I can get it really hot, the compost is made quickly. Otherwise, I have to keep adding greens over a period of time and that slows the process. But I do like the Mantis. I have 3 going now.

I am of the opinion that the doors should face downwards. Another user on this forum faces the doors upwards. Water should not leak in. havent seen water leak thru a standing seam, has it separated? Anyway, tumblers are easy to over water, I keep a mental note on how much water i add and adjust subsequent loads accordingly. Using primarily leaves and coffee grounds I can average 1 load per month (using the single bin tumbler).

good luck

Yes, tumbleness, I agree with you, and that is my argument with Mantis. If the doors are facing down, which would not cause any problem, then the air vents are covered with compost, restricting the air flow. The owners manual even says not to have them restricted. I suggested to Mantis to put the air vents on one of the panels on either side of the door, which would now be higher up if the door is facing down. The door should have only drainage holes in it only. Then I feel the unit would be a winner. One of the seams is a loosly connected seam, meant for expansion & contraction. With the door facing downward, you are right, the water would not be able to flow into the unit, but the unit needs the extra air ventilation that is presently in the doors, plus the vents on the side caps. I have been trying to get them to make a door with only drainage holes, and one of the other panels with the wents in it, but they keep avoiding my request. So I have a piece of plastic tied over the top of my unit to keep the rain water from running in.

do you feel that the "end cap" vents are not doing there job? I hadnt thought about this before: a single drum would have some sort of cross air current, whereas the the twin has the divider panel between the 2 vents. i dont know if this has any impact. I agree that these tumblers could use tweaks. Aeration is achived by the tumbling action, turn when the pile is below 120F and turn when over 155F. I found that over filling was not good as it interferred with mixing when turning and would block side vents.

as I mentioned, I was told that when the doors face upward, water didnt leak in significantly. as far as an open seam (I dont have one on my ComposTumbler) I would be tempted to seal with a green caulking.

When the load get too wet it is difficult to correct that. Adding dry browns will help a bit, but that will throw your C/N ratio off. Sometimes it is simpler to dump it and start over. The tumbler retains water efficiently.

compostumbler

According to the website of the Compostumbler (click on "How it Works") the door is parked in the down position with air flowing in thru the door vents and out the side vents. Not sure if the Mantis is the same. I know on my homebuilt tumblers, when they are hot, the natural convective heat rising, draws air in through the bottom, through the compost and out the top. On those cool, calm mornings one can see the columns of warm moist air rising from the vents. I would suspect these other tumblers would act in a similar manner. I wish I had one to try out, they look like good units.

Lloyd

Here is a link that might be useful: Compostumbler

I have the twin tumbler also. But if you went to the one link you know that as those are my photos in there. I was getting the same problems you were having till I put in the cross bars. If I do get lots of rain I do find the batch gets a bit wet but after a few turns, a day or two with the doors open it will dry right out again. I have thought about building a small shelter over it, but it has never been a big deal.
I would worry your tarp would also be stopping the air flow, which would help somewhat on drying it out. Mind you this is a closed system. Water won't get out of there like in an open pile. So if you put lots of wet stuff in there it will be hard for it to dry back out. It is really tricky to get it just right.
Sandy

Sandy,
So whats wth the "expansion" seam that rocklandguy had mentioned on the mantis? does positioning the drum have to do with this? (to avoid taking in too much rain).
For some reason I had saved a link to that thread, posted it thinking rocklandguy would find it useful.
For some reason search does work in this forum for me.

take care,
nes

Hi nes, I read your link and the second posting by brdldystlu showed the expansion joint that I am talking about. Mantis says that that is there for expansion and contraction and also an "out" for excess water as you turn the unit. Boy that was a long thread, but informative. Also PT03's link, clicking on "How it works", might be telling me what I am doing wrong. That shows a single unit, I have the double, but it is the same principal. The Mantis Twin-Composter justs gives you the ability to work two loads at once. It shows the doors with the incoming air vents facing down. That diagram says they double as air vents and drainage units. Then the side vents are postioned at 12 o'clock. Lloyd is right, the air would be DRAWN IN from the bottom, thru the compost, and the hot air would FLOW OUT the top side vents. If this is correct, then the so called expansion joint (the two panels loosly connected) would be overlapping in the correct direction where rainwater would run off, not into the unit. Then the only rain water that could enter is water that would follow the drum down, under, and go in either the hinge side or the latch side of the door. Then it should flow UNDER the compost & OUT the drains, not saturating it by flowing on top and thru the compost. Yes, that makes sense. The owners manual says "Occasionally, check the breather screens in the doors to make sure they do not become CLOGGED". I took that as not having them BLOCKED. I will have to try that. I don't know why Mantis couldn't just tell me this when I was going back and forth with them for days? I still think this is a great unit if we just knew how to work it properly! But everyone here is great! Everyone tries to work towards a solution and helping each other. Thanks everyone!

I am trying to remember about the expansion seam, I am thinking there is one. I always park my tumbler with the doors at the top. If we get days of rain sometimes the compost does get a bit wet. But mine seems to drain, I keep a pan under it to catch the drippings. But for the most part I don't have a huge issue with lots of drippings. I do try to make a point of turning it at least once a day, and I crank it a full dozen turns a day. I figure the more I mix it the better. Right now mine is a bit on the dry side. It is a closed system so I use to have issues with it being wet. Then I learned to not add any extra moisture.
Sandy

rocklandguy,
i think the point is, too much water will defeat the composting process (or at least slow it down to make it impractical). Do what you can to solve this. When things are working right the pile should be well along towards compost after 2 weeks. If I can do this, then anyone can!
I know you have leaves, but what are you using for green? as for myself, we dont generate enough kitchen scrapes to heat the load and have to resort to Starbucks for our primary green this time of the year.

tumblenes, I feel my problem is all the water getting into the unit. Now, during the winter, all I have is kitchen scraps, ie coffeee grinds, banana peels, potatoe skins, carrot peels, pieces of fruit & veggies; basically whatever we can find. Between the paper, plastic, & glass recycling, and the composter, we hardly have any garbage anymore, which is a good thing. We have this stainless steel container on the kitchen counter that holds alot of kitchen scraps and when it is full, it goes into the composter. During the rest of the year, I have all the grass clippings and yard waste that I need.

Hi Sandy (brdldystlu) - I just checked my Mantis Compost-Twin with the doors parked in the "up" position and that leaves the so called "expansion joint" on the side for rain water to run down the sides and in, not to mention the rain water that is entering straight down thru those vents. So far, the idea offered of the doors facing straight down seems to be the right way. I will have to try that. Paul

Maybe the door position is not that critical. I am of the opinion that 4 weeks in thumbler is long enough, 2 if you are impatient. i know you twin guys use that tumbler for storage, I do not. So these are time from the initial temp spike of 150F or so (about 12 to 24 hrs after mixing a full load.

IÂve been trying to think of a good compost recipe. I have to make assumptions on how big one chamber is on the twin. Here it goes: 1½ 30 gal garbage cans of shredded leaves, 5 gal kitchen waste, 10 gals coffee grounds, 2 gals water. How does this sound?

One advantage of coffee grounds is that they mix well with the browns. Shredding the kitchen waste would help if you have the means.

Remember, a garden has an almost insatiable appetite for compost.

I would hazard a guess that placing the doors/vents in the down position does two important things that are sort of related. 1) Prevents any extra moisture from entering and 2) aids critical airflow through the material. That is, from the bottom to the top. Doors on the bottom would facilitate this, more so than having them on the top. I would think that putting the doors on top would just bring the air in through the side vents and then up not passing through the bulk of the compost.

It seems with my tumbler that once the material is in the tumbler and close to being properly moistened, the fresh air getting in and flowing through the compost is critical. In fact, once I can get the temps up into the 140-150's (usually next day) I have to add moisture about every third day. I am assuming this is a result of of the warmer moist air coming out through the top vents. As the temperature begins to subside after 10 or 12 days, less water needs to be added to the tumbler and the temperatures begin to hover around 105-110. It is at this point I take the material out and put it into a curing bin and a new batch can be started in the tumbler.

Lloyd