Building a Home Mud Pit - what to use

[Sydney]

This isn't about the making of the pit "structure" per say... My wife and I bought a house a few years ago. We're in a pretty arid area - not a desert, but pretty dry. Any thoughts on lining a pit, and what to fill it with, so it either remains sinkably soft... or can be quickly reconstituted?

[Fred588]

For a liner I would recommend a nylon-reinforced vinyl tarp, but one that is at least 8 mils thick and preferably 10 mils thick. You can get them rather cheaply at only 5 mils but one that thin will be holed very soon - possibly on arrival. Make sure there are no protruding roots, sharp rocks, or other things in the bottom or sides of the pit that could poke a hole. Fill the pit with water only at first and let it sit for a few days to be sure there are no leaks. What you will it with is, in my opinion, a matter of personal preference, intended use, and, obviously, your budget. If the actual volume of the pit is, say, three cubic yards (4 X 4 X 5 feet) you will need almost that much peat moss if you choose peat moss. Its impossible to give an estimate for bentonite clay without knowing your preference for viscosity. Whatever you use for mud, add it slowly. Otherwise you may have trouble getting it fully wet, especially with clay. With peat you have to enter it gradually as it will float initially and what looks like an over-filled pit will turn into almost pure water (well, murky water) in a day or so.

This isn't about the making of the pit "structure" per say... My wife and I bought a house a few years ago. We're in a pretty arid area - not a desert, but pretty dry. Any thoughts on lining a pit, and what to fill it with, so it either remains sinkably soft... or can be quickly reconstituted?

[quickman]

You can get a big piece of black pond liner from Home Depot or Lowes. Gardening section

[mudxdresser]

I would recommend using above ground swimming pool liner. I used that in an indoor heated mudbath for decades and never had a hole develop. To avoid holes outdoors, just make sure that there is no slack in the subsurface that the pool liner is installed in. If there is any give at all in the dirt or whatever, fix that before proceeding with something like concrete, packed clay, or even thin wood or plastic.

Swimming pool liner can be found at pool supply companies. If you find it to be too expensive, you can instead usually find used above ground pools for sale cheap after their owners tire of them or they get holes in them. Buy you some industrial grade vinyl glue and you'll find that a properly applied double patch on both sides will be stronger than the original vinyl.

Good mud/clay is expensive, protect your investment and lower your maintenance efforts in removing debris from your mudpit by doing two things. Put a cover over your mudpit and provide a lip or some such for it to assure it stays in place and keeps dirt, dust, and other debris out. Second, provide a clean landing area on one side of the mudpit with something like plastic or wood to use as an entrance/exit point. Equip the landing area with a chair and some water to wash your feet with prior to entering the mudpit.

[Mynock]

Another option would be a pond liner (for building fish ponds). Little more expensive but very durable. I've seen people pour rocks into a newly lined pond with an excavator bucket with no ill effects, and they're designed to last for decades.
Good luck! I've been dreaming about doing this for years. If not too much trouble throw up some pics of the construction process!

[Sydney]

We'll see... I do have to actually discuss it with my wife, but it's also not necessarily likely to happen this year. I'm hoping for next year. Right now we have other projects, but I appreciate the inputs.

[maria]

What's the best way to keep the mud moist and sinkable? Are there any ways without using expensive pumps? If the pit is covered, and filled with bentonite, how long would it stay liquid enough to sink into?

Do combinations of peat and clay work well for keeping moisture in the pit?

[Fred588]

I have both bentonite clay and peat pits here at Studio 588. Both have been in existence for well over a decade, although the peat pit has been dug out to replace the liner twice in that period. Both are covered from September through early May but left uncovered during the summer. Pumps are not used in either except that the clay pit has a recirculating pump that moves hot water through about 100 feet of hose located at the bottom. But this is for heating - no mud is moved.

How long a pit will stay wet will depend on how much water is added and how much is lost. The loss, however, will depend on several local factors. It will dry out more quickly if you are in a hot, dry location. That should be obvious. It will also dry more quickly, if you do not have a liner or if the liner leaks, if the ground is very porous and above the water table. My clay pit does not have a liner at all - the clay tends to self seal (EXCEPT very near the surface when it starts to dry out). Bentonite clay Is used commercially, in fact, as a lining material for farm ponds, although its proper use as such requires that the slope of the sides of the pond not exceed a certain value. I don't know what that slope value is but I would get about 45 degrees. I have to add as much as a dozen bags of dry clay every spring to replace some that is lost near the top in this way.

One thing to definitely NOT do without careful study and experimentation is to try to use ordinary soil, even bagged topsoil, to make the mud. If there is any sand in the soil (and bagged topsoil is probably at least 30 percent sand) all the sane will sink to the bottom as soon as it gets wet enough, thereby reducing the depth of your pit.

I would advise against trying to mix different materials, such as clay and peat. That sort of thing might be interesting for a pit to be used for filming but for recreational use I expect it would be disappointing. I tried it once before Studio 588 was built, thinking the peat would accumulate at the surface and form a thicker-looking crust but it did not work that way.

What's the best way to keep the mud moist and sinkable? Are there any ways without using expensive pumps? If the pit is covered, and filled with bentonite, how long would it stay liquid enough to sink into?

Do combinations of peat and clay work well for keeping moisture in the pit?

[Mynock]

The sloped sides are an interesting concept, because my dream pit would be fairly deep (I was thinking 6 ft). Digging a funnel shape with a small "max depth" spot in the middle instead of trying to make what amounts to a swimming pool would substantially lower the volume, which would make the cost of your sinky material of choice way cheaper.

[Fred588]

The sloped sides are an interesting concept, because my dream pit would be fairly deep (I was thinking 6 ft). Digging a funnel shape with a small "max depth" spot in the middle instead of trying to make what amounts to a swimming pool would substantially lower the volume, which would make the cost of your sinky material of choice way cheaper.

This is very true. Have you confirmed that you have that much diggable depth? Here at Studio 588 the ground turns from rocky to layered rock at about 2 feet and one encounters the planet Earth at about 5 feet.