Wisconsin cabin modernization

Hello!
Need some advice regarding a cabin's plumbing design.
It's a ~10 year old 30x20 log cabin on piers in southern WI. Just buying it, and currently no electric, plumbing, etc. Nada.
So, in '10 the plan is to drill a well, bring in septic and electric. No plan to do central heat, just the wood-burning stove.
I have plenty of plumbing experience in traditional, year-round homes.
But this place will be vacant for most of the winter, with a possible occasional weekend visit for winter fun, but I am on unfamiliar turf with the need to winterize and the lack of a basement...
What is the best design for this situation in terms of ease-of-winterizing? How is the 3 foot open-air gap between the bottom of the home and the earth dealt with in a way that allows occasional sub-freezing use?
And is this a good situation to bring in a tankless H2O heater?
Thanks in advance.
-S

I would make sure there is a slope on all water lines so they will gravity drain. You can just install a drain valve in the end of the line. The water pump will need to be protected as well. Of course, sewer lines need a 1/4" per foot slope for drainage anyway. I would close the space around the house to seal drafts. I am not a fan of tankless water heaters. They are extremely expensive to install and operate. You would need a fairly large one for winter use. A propane heater would be a good choice because of the rapid recovery, but an electric heater would be OK, too. When leaving during the cold weather, you would need to drain the water lines, hence my recommendation for gravity drain. Traps would need to be winterized as well with RV (not automotive) antifreeze. That includes the toilet trap. Be sure to drain the toilet tank. The water heater would also need to be drained. If there is doubt about draining the water lines by gravity, then an air compressor would be needed to blow them out.

Gary-
Thanks...how do you deal with the unheated part between frostline & interior? do supply pipes there need to be heat taped/cabled & insulated in order to use in winter?
Do I need a pit below frostline?
-S

Any water pipes sitting out in below freezing temperatures will freeze. If there's a breeze to help move heat away, they'll freeze faster. First thing I'd do is check with the building inspector to see how deep the frostline is. That will give you an idea of where you want to run your pipes, depending on where you drill the well. You'd probably want to bring the pipes inside the cabin as soon as possible and find a way to run them inside rather than relying on hanging them out in the breeze in sub-zero temps. That way you'd only have a short vertical section to keep warm. Drain pipes don't usually have moisture sitting in them except for the traps, so you may want to think about how to do the shower, since it's trap would normally be below the floor. Boxing it in and insulating may let enough heat from the cabin keep it from freezing while you're there, but you'll need to keep a suppy of RV antifreeze around to fil the traps when you're not there. I'm sure the pros will have more ideas and best practices. Could you enclose the bottom of the cabin? Just keeping out the breeze would make anything you do easier on the freezing issue. You'll want to consider installing some fittings so you can easily blow dry the lines. this will require a small air compressor, or a portable tank you can fill at a service station and bring with you.

Jim, Appreciate the advice.
As far as fixtures, this place will be pretty simple...Kitchen sink, Shower, toilet and probably a bath sink.
Is PEX a good option for me? I've never worked with it, but the idea of some 'insurance' in case something does not get drained properly is appealing.
Thoughts?
-S

....and now that I think about it, a washer & dryer may need to be part of the picture as well, but that has me wondering about the washing machine freezing. I suspect that could be a serious problem. Are washers drainable?
-S

The washing machine will be a real PITA to drain. I have had them get frozen with out damage but I don't think I would rely on that. I may have gotten lucky.

As for pex. The pipe it self can take a freeze. I used it in a crawl space for that reason. HOWEVER there are 2 potential problems. The fittings can not take a freeze if they are full of water. The second problem is if there is a sag in the line it will hold water and is guaranteed to freeze.

If it were me I would put ALL of the pluming in as small of area as possible. For example:
in one room put the washer/dryer, LP water heater, well pressure tank. Also heat this room with a small LP heater. Common to one wall (or in the same room) put the bathroom. Common to another wall put the kitchen sink. Keep the pluming common to the heated space. Also set up the pluming so it can all drain back to the utility room. Insulate this room as well (keep the pluming inside the envelope.) Insulate and heat tape the line coming up from the well. The goal is to keep the water inside an insulated heated space. Keep the heater set for 40 to 50 deg.

I would still drain the lines as much as possible and use RV antifreeze in the traps. Especially if your going to be gone more than a week or two. ALWAYS turn off the main valve. By cutting the heated space down to less than 100 square feet and keeping a low temp it should cost very little to keep it above freezing.

Freezing of the the water line between the frost line and the inside of the cabin should be a concern. You can't count on having reliable electricity all winter so heat tape is not a good solution. For all the camps I maintain we use curb stop/drain valves. Using the T handle that comes with the valve you can easily drain the vulnerable section of pipe. You just have to be sure to lock-out the well pump do that it is not turned on while the stop/drain valve is in the closed position. You can get these valves of varying length to accommodate depth of frost for your area.

I agree on the low-heat solution...and acknowledge that it is very likely we will lose power here and there...very rural.
The below-frost valve seems mandatory. Do these require a pit, or are there versions that require no access? And how does the drain aspect work? Do they drain into an underground bed of gravel or something?
Any manufacturers to recommend?
Thanks,
S

The valve is installed at the time of running the water line and other than access to setting it up no "pit" is needed - as a matter of fact you want it buried so that frost can't get to it. At the point of the valve dig out 6 or so inches of the soil and replace with 3/4 or 1 inch stone and set the valve on it and around it to support it after you have made the plumbing connections. Google Curb Stop Valve and with that you will be able to see pictures and sources. The valve system comes with a long neck that extends to the surface. It comes with a flared flange and a pentagon nut that keeps the column clear of dirt, etc. A T-handled wrench comes with them do that you can turn the 1/4 valve on and off. In the off position the valve opens to allow the house side to drain back into the stone while the well side remain turned off. Since the valve is in the low position it is a great way to drain the main line from the house.

Good luck.