Im designing a semi passive solar house. initially it was to be a crawlspace but Im beginning to really like the idea of a slab thermal mass for passive solar heat storage in the winter. . where I live we have a very expansive clay soil that can cause problems with cracking slab foundations etc. Im trying to look into the future when repairs may be needed. in a two story house, where the only plumbing downstairs would be for a powder room and a kitchen sink, do you think it would be possible to design it such that there would be no plumbing going through the slab? . my uneducated thought is that if these two items are next to an outside wall, you can raise the toilet and have the plumbing go outside instead of through the slab . . . thoughts and ideas are appreciated

for some reason my post is not showing line breaks. Sorry about this

You COULD. But you'd basically have to raise the level of the floor.
This would negate some fo the benefits of a thermal mass concrete floor?

Don't worry about Schedule 40 PVC drain pipes or PEX water supply lines passing through the slab.

I agree with arkie6....plumbing in a floor is not a problem....just plan it out....millions of houses are like this.

What is it that you don't like about it. The supplies can come from overhead so the drains is the only real potential issue.

Good Luck with your project.

Plumbing doesn't need to go thru the slab. Use a upflush toilet, sink system.

Right, there is no reason for any plumbing to be below the slab except for maybe waste drain pipe, combustible device intake air pipe or maybe hot/cold domestic water pipe if you have a kitchen island with a sink (but run this through a chase with access in hollow interior walls so it can be easily replaced if ever needed). Keep the areas that require waste drain pipe close to the exterior walls and run this pipe perpendicular to the wall directly and straight outside so that if they ever have to be replaced it is a relatively simple matter that won’t require jack hammering the slab. A little thought and planning will go long way in eliminating any future headaches. Crawl spaces attract bugs and rats and are not a good place for humans to work, so they are always avoided by good and smart builders like the plague!

You might want to put some electrical chases under the slab to connect the service panel to any sub panels and to get power to a kitchen island.

You might also want to consider hydronic radiant floor heating as it would likely be the lowest acquisition cost and most comfortable way to heat your first level space since you are already pouring a slab. It can also be the most efficient and lowest operational cost if you use an air to water electric heat pump or a mod con gas boiler as the heat source. And be sure to work out the passive solar monthly BTU loss/gain numbers for your specific location and building design so you adequately use passive solar heating but without ever over heating the space. We have lots of info and free calculators on our website for figuring all this stuff out.

thank you guys!!! I asked this question on another forum and I got crickets.

Diletantte, I was thinking of just raising the floor under the toilet, since the sink drain plumbing is high enough to go directly out the wall

Arkie6, thanks but why do you say that. My buddy just had to spend $2800 to fix a broken pipe under his house. thankfully they dug under the house and didnt even have to jack hammer the slab.

Newbostonconst, thanks. when you say plan it out. can you expound a little?

Smartwall. I had never heard of that. thank you. I will look into it. although if I can avoid it that would be best but its still a great alternative.

Sailawayrb. THANK YOU. I have looked at heat loss, but not really heat gain . I need to do that to help me size my windows.

I appreciate the feedback all

Plumbing code now requires sleeves in slabs on grade. Slip the pex through with connections accessible on both ends. That said, Texas doesn't do much inspecting unless things have changed.

Plumbing code now requires sleeves in slabs on grade. Slip the pex through with connections accessible on both ends. That said, Texas doesn't do much inspecting unless things have changed.

Plumbing code now requires sleeves in slabs on grade. Slip the pex through with connections accessible on both ends. That said, Texas doesn't do much inspecting unless things have changed.

Yes, plumbing code has required sleeves for many years for everything that passes through concrete (e.g., footings and steam walls, etc). However, I don't think they require chases for plumbing pipes under slabs (but not in concrete) like electrical code requires for wire. Nevertheless, it is always prudent to use chases wherever you can as it provides an opportunity to remedy a failure without jack hammering the slab.

I'd avoid running pipes under the slab and particularly so in Texas. While pex seems durable so far, predecessors such as polybutylene have created some nasty situations. The risk is exponentially higher in Texas because expanding clay raises hell with slabs on grade. One hopes OP has asked locals if a soil boring is warranted. In San Antonio, the city sued PolyB manufacturers. Sleeve water service into the house, preferably to a manifold. Route pipes through the walls and ceilings. I have one extra sleeve in my house connecting a sink in the kitchen island. You'd risk freeze damage in one-story ceilings although the risk is small in Texas under a foot of cellulose. Running pipes in a north facing exterior wall is riskier. A design that tightly groups baths and kitchen minimizes cost, connections and ultimately problems. Its easy to do in a two-story. In a one-story design, separating bedrooms and concentrating baths are conflicting goals.

Yes, all very good points to consider. PEX in a chase should last forever and using the chase enables relatively easy repair if ever needed. We don't see extreme cold in southern OR and generally if we have a slab floor build, it will also be HR eliminating the freezing risk. Bottom line, when putting something under a slab, always first think about how best to enable repairing it with minimal headache...

Well no matter what unless running the piping on the exterior of the home you will be penetrating the slab for the soil stack typically the slab will not be sitting directly upon expansive clay and will have gravel and or sand under the slab portion. I suggest running copper water lines in the slab even if the cold water lines absorbers some latent heat it will be added a bonus as you will be using the sinks for washing dishes or hands anyway. If you have a concern with the copper pipe is in the slab corroding wrap it with visquin or buy a roll of pipe sleeve made out of the same (my house is almost 60 years old and still no in slab water leaks to date). Don't forget you will also be putting hose bibs on the exterior wall as well. When a break happens typically the line is abandoned and rerouted through the attic to an interior wall or (T) off of the existing line in this case running through the floor joist.

Find a licensed plumber in your area that has been in business for years, they are my go-to resource as so much of plumbing code is tailored for each region.

Here we are pile supported due to nonload bearing soil and use pipe hangers to prevent separation in your sewer lines when the soil retreat. On the reclaimed marshland here my yard moves up and down depending on the water table.

Another tip while the inwall piping will be in PEX for economic reason, have all of the stub outs through the wall as copper for ease of fixtures installation.

Expansive clay does its thing proportionally over its depth, which was 12 feet under my slab outside Dallas. They put cushion sand under the concrete but it would be zero help if a leak was wetting a portion of soil under the slab. Pilings work, or avoid putting pipes in or under the slab.service entry is easy to access. Again OP's site is unique and he should consult locals. The

Expansive clay does its thing proportionally over its depth, which was 12 feet under my slab outside Dallas. They put cushion sand under the concrete but it would be zero help if a leak was wetting a portion of soil under the slab. Pilings work, or avoid putting pipes in or under the slab.service entry is easy to access. Again OP's site is unique and he should consult locals. The

hi all,

this is the floor plan. If I raise the floor of the downstairs bathroom, is it feasible that I can have no plumbing in the slab?

downstairs

downstairs



upstairs