4 inches PVC pipes are mostly used for toilet waste pipes and before installing this pipes it’s necessary to check if they are of good quality, also check if there is any cracks and also not exposed to too much sunlight before you get them.
If your pipes has been exposed to sunlight for long and has been weaken by long term exposure, the pipes will hardly be watertight and can crack easily when it comes under intense pressure by external forces.
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Can Toilet Waste Pipe Run Under Floor
Yes toilet waste pipe can run under the floor hence you can run your toilet waste pipes under floor and you wont have any problem.
If you choose to run it under a concrete you will need to cover it with sand, plastic or form wrap as this will help protect it from direct contact with the cement which will help in the long run, preventing it from failing.
Please note that PVC and concrete are not meant to come in contact. If you should to pour raw cement over your toilet waste pipe then there will be no room for expansion and contraction needed at some point.
If your toilet pipe cant shrink and grow with the temperature or season it won’t just last, it will crack sooner.
Does A Toilet Waste Pipe Have To Be Straight
No your Toilet waste pipe don’t necessarily need to be straight because of the solid that it carries along with the water hence your toilet waste pipe has to be sloppy.
Your toilet waste pipe has to be sloppy to allow or enables water carrying solid waste to flow easily. We have discussed how sloppy it should be below.
How Much Fall Does A Toilet Waste pipes Need
A toilet waste should be 4 inches pipe in diameter minimum, this is recommended to allow it accommodate enough solid waste.
Again because of this solid waste which often comes along the water there is a recommended maximum and minimum slop that must be adhered to.
how much fall does a toilet waste pipe need depends on so many factors such as the length of the pipe etc. But what does the plumbing code requires? Well the plumbing code requires that every toilet drain pipe should slop at not less than 1/4 inch per foot and the maximum slop should not exceed 1/8 inches per foot.
Please understand that your pipes will usually handle water that are mixed with some solid hence getting the right slops will ensure that your waste flows along with your solid.
If you decide the fall of your waste pipe to be below 1/4 inch per foot then you are going to experience clogging because there wont be enough velocity to push the waste.
When there is fall above the maximum then water will likely separate from the solid waste because the water will always run faster than the waste.
What Angles Should A Toilet Waste pipes Be ?
The most important point to note here is that your toilet waste pipe should be on a downhill gradient!
What we mean here is that it should fall gradually and The “fall” or “drop” need to be based on universal applications plumbing code which allows for between 1/4 inch minimum and 1/8 maximum for a 4 inches waste pipe.
You don’t need to go Too steep like 1/10. if so the water is likely to runs quicker living the solids behind. What this means is that your solid wont be washed down the drain pipe.
If you decide to go too shallow like 1/2 then there will still be a problem, there wont be lot of velocity to move the water and the waste alongside
How deep should a toilet waste pipe trench be?
Here comes another interesting question as to how deep should your waste pipe be buried under the soil.
Before considering how deep it should be, you have to consider your climate as this hugely influenced how deep it should be. If your climate is cold or you stay in a cold weather region then you should consider going deeper to prevent your waste pipe to be completely frozen when it snows.
On the average you have to dig deep enough to an extent where your toilet waste pipe is buried completely under the soil.
Let’s says around 12-24 inches-deep, this should comfortably house your 4 inches waste pipe.
Like we said if it’s a cold climate region you should go deeper to ensure frost protection. Also take into consideration that you don’t go beyond the level where it will difficult to access the pipes for repair in future.
Are All Toilet Waste Pipes The Same Size
All toilet waste pipes are not the same size but it is highly recommended that 4 inches pipes are used instead of 3 inches pipes because 4 inches pipes are wide enough to allow easy flow of solid waste.
Again 4 inches pipes are capable of carrying enough liquid twice the size of 3 inches pipe. 3 inches pipes are mostly used for kitchen drains etc.
how many toilets can be on one soil pipe
Understanding how many litres your pipe diameter will contain is the crucial here.
Ideally a typical toilet pipe should contain or accommodate up to 6 litres/sec,that’s its maximum capacity .
Ideally 4 inches waste pipes can support 90 DFU’s
Can You Run Waste Pipe Through joists?
Its not recommended that you run your waste pipe through joists straight with out cutting it into joint, any attempt to do that should be avoided
drillings on the joists are known to compromise or rather weaken your drain pipe on the long run.
If you must run your waste pipe through the joints then first you need to cut it into joint like we said before. Make sure you drill your joists properly to fit your pipe.
You now have to cut your pipes into section (make sure that each section fits into the joists base). Don’t forget, you might need couplings which makes it easier and get the job done.
Sources
https://epubs.iapmo.org/2018/UPC/
https://www.bhg.com/home-improvement/plumbing/plumbing-codes/
https://www.phcppros.com/articles/1902-code-requirements-for-drainage-system-cleanouts