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From Texas-sized 2 Tiny House For Three

Tiny House Plumbing 101: The Research Phase

I’ve been getting a bit cross-eyed over here trying to tack down the resources we need to plumb our tiny house the way we want to, which is to have access to both city water (aka “pressurized water”) or be off-grid using a fresh water tank for the supply (RVers call it “boondocking”). I already knew that would entail having two different ports, for lack of a better term, that allow water to either fill the tank or bypass it and go directly into the faucets or water heater, but having a split system like this doesn’t seem to be a super popular choice with the tiny house community thus far any way.

I found some great articles about plumbing a tiny house like these two HERE and HERE, but all the ones I found mostly focus on going all off-grid OR all pressurized. THIS POST from Tiny r[E]volution has probably got the best compare & contrasts of pressurized vs. off-grid tank systems of the actual tiny house websites I’ve found, and it and THIS POST from A Bed Over My Head actually made me realize I’ve been looking in the wrong place for this info! We should research from actual RV info sites since that’s really what we’re trying to replicate anyway.

It should be briefly noted that I’m excluding any discussion of toilets and black water needs because we already know we’re using a composting toilet, so all I care about for our purposes are fresh water hookups and and draining to gray water tanks.

Anyway, the Tiny r[E]volution article had a link to THIS SITE, and after reading through it I did a google search to find an even more helpful (for me anyway) post on MarxRV.com aptly titled, “Water, Water, Everywhere!” As I’ve probably mentioned before, I am a visual learner and prefer to have images (and in the best situations, actual hands-on time) of whatever it is I’m trying to learn about. The post includes photos of connection components and a cool little diagram that effectively dumbs down basic RV plumbing setups for the clueless folks like me, and I’ll try to add some more here for your own visualization of what I’m discussing.

Based on the current interior layout we have in mind (pic inset), it looks like the most logical place to put the fresh water tank will be in a compartment we create under where the refrigerator will sit on the wall that divides the kitchen from the bathroom. That way it will be inside the building envelope and well insulated. Since the primary reason we put the kitchen and bathroom up against each other was to make plumbing as simple as possible, I’m also happy to see that most of the fresh water ports with both gravity fill holes and city water connectors (I’ve seen them called too many names to list, but port makes sense to me) have the gravity fill on the left side. 02newlayoutMy thought is to month that essentially centered to the wall that will divide the kitchen and bath (making allowance for wall studs of course) so that the pipe from the gravity fill is short and goes directly into the fresh water tank without having to snake through the walls. That also means the city water port will hopefully line up pretty well with the bath wall so we can connect it to some PEX piping. From there the city water inlet will connect to a PEX pipe coming out of the fresh water tank on the other side of a 12V water pump we’ll have to install under the kitchen sink to pump water from the tank when we’re off-grid, and then that pipe will go directly to the hot water heater on the tongue end outside wall. That same pipe will also have to split off twice to feed the cold water of the kitchen sink and the shower, but those splits will be very, very short considering how close quartered all this will be. The only long runs of PEX will be to and from the hot water heater, and even then it will be less than 8-ft on the outside wall of RAD’s bedroom and the bathroom.

As for drainage, I think we can simplify this a bit, too, with some careful planning. Since we’d want to keep the house as balanced as possible, particularly while traveling dow the road, my thought is to install a gray water tank of equal or slightly larger capacity on the opposite side of the trailer underneath it to allow gravity to drain the kitchen sink and shower basin. I also think it needs to be a pretty shallow tank, so I’ve found one that I think will work at only 7″ deep and 42″ long. If we were to lay the two tanks, fresh and gray, end to end they couldn’t be collectively longer than the trailer itself is wide, but since the gray water tank will rest under the trailer, though, it can be any length less than the trailer width. It won’t need to be that long, of course, but it could be. I’m also thinking of off-setting the gray water tank closer toward the tire axels to center its weight a bit more since both tanks will have to be mounted on the tongue side of the axels. My thought is that when both tanks have liquid in them if might help balance the trailer a bit, particularly since the kitchen side of the trailer (the right side if you’re looking at the front door) will be heavier than the other side. Maybe moving a little of that weight back will counterbalance it a bit, though I could be wrong about that of course.

Anyway, I think we could drop the kitchen sink drain down to a p-trap and back into the wall behind it to meet up with the shower drain that will essentially drop straight down to a p-trap under the trailer and then horizontally a short distance to the gray water tank. I think the sink pipe could connect to the shower pipe just before the shower one enters the tank on the side closest to it (the side facing the tongue). We’ll have to figure out how to strap the tank to the trailer itself, and I’m thinking we might just hire a welder to make custom a “cage” of some sort for the tank that would be sturdier than anything we could probably fabricate ourselves. The drain for the gray water tank will have to be on the opposite side of the house (driver side of the trailer when hooked to our truck), and I’m still contemplating adding a second spigot that could connect to a small piece of soaker hose that would in turn be set in a pot layered with gravel, coffee filters, and soil to become a portable gray water filtration system for times we are able to drip gray water out vs. dumping it at an RV station.

There’s much more rumbling around in my head about the plumbing, including some photos I’d like to add, but I have a rambunctious 2.5yr old begging me to go with him and his DaDa to the park to see the choo-choo train playground they found recently on a bike ride. Guess there will be a Part 2 on this post! 🙂

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