Minimum plumbing slope for drainage?

[Daox]

I'm trying to figure out the tank to solar panel slope I'll need. I believe the general rule is 1/4" every foot. Is it possible to get away with less than this?

[AC_Hacker]

Originally Posted by Daox

I'm trying to figure out the tank to solar panel slope I'll need. I believe the general rule is 1/4" every foot. Is it possible to get away with less than this?

1/4" to the foot is the minimum.

-AC_Hacker

[AC_Hacker]

Originally Posted by myra

All of your drain pipe must slope slightly downhill. Usually 1/8”per foot is plenty for drainage, this is the same as the commonly recommended 1% slope.

Code in the US is 1/4" per foot... 1/8" per foot may be ok in the UK, but 1/4" per foot minimum is code in US.

-AC

[mrd]

The code required slope for drainage pipes is specified to maintain what's known as a "scouring velocity" - this is to keep solids in suspension and prevent accumulations. The Manning formula - Wikipedia, the free encyclopedia would be the formalization of this. International Plumbing Code specifies 1/4 inch per foot minimum slope for pipes <3", and 1/8 inch per foot for 3-6" pipes.

Do you need to be concerned with solids in suspension?

[Daox]

Thanks for the update mrd.

I do not have to be concerned with solids suspension. The question was in regards to for a drain back system for a solar hot water setup. In the end I decided to do a pressurized loop instead of a drain back just due to the grade of my land.

[peteinspain]

standard plumbing falls are 1 in 40 for 4 inch drain (2.5%) and 1 in 60 for 6 inch but any fall for liquid is ok if its just water and time is not an issue

[AC_Hacker]

Originally Posted by peteinspain

standard plumbing falls are 1 in 40 for 4 inch drain (2.5%) and 1 in 60 for 6 inch but any fall for liquid is ok if its just water and time is not an issue

There are three issues here, one issue is the physics of the plumbing solution, the second is the international code that applies to the plumbing solution and the third is the local code legality of the plumbing solution.

International plumbing code does not legally superseded all local plumbing code.

I know this to be true in the state where I live, Oregon, USA.

Here, although physics and International Plumbing Code would allow lower slopes, local code specifies slightly greater slope, and construction cannot legally proceed until a local inspector, who is bound by the local code, approves the particulars of the installation upon inspection.

I fully realize that DIY and legality may diverge, so it is wise to be aware of all aspects of the situation.

-AC_Hacker