Angle of the Slope for a Waste Pipe

As a general rule, allow 1" in 10' (1:120) and it ought to be OK. Local building regulations may offer different advice/requirements. It is possible to go shallower, though not recommended for the unsavouriness that may ensue...

Thanks for that PW, I can carry on digging now! Or I may go to the shed and play with some radioactive stuff! I enjoyed that story too!

My pipes run at 1:100. Would You suggest I lower the house by 13mm ?

As a matter of fact I can't remember the slope (Done in 1970). I had to install a ski jump to keep the slope flatter.

Sloping to fast is also bad. The water tends to rush away leaving the stuff high and dry.

Always best to have your bath outlet to the waste pipe uphill of your toilets this gives the unsavoury matter a bit more impitus and keeps things sweet.

I think that a few more details may be required here.

What is the pipe made of

What is the diameter

What is the waste - bath or foul water etc.

How many bends of what angle are there?

I use the 1 in 40 rule for most 40mm and 100mm plastic pipes without too many bends when installing bath, kitchen or foul water pipe.

If the 100mm pipe run is long and very straight and there are only a few joints - we try to use 6 metre pipe lengths, then I will go up to 1 in 80.... But no further.

The usual problem if you go flatter is a buildup of papers of various sorts on a joint or bend which is not flushed away by the water.

OK you guys, you asked for it!!!

On Monday I ate for breakfast my toast with marmite washed down with a cup of coffee, then in the afternoon chicken stew, very nice! Tuesday morning, toast and marmite again, then an evening meal of prawn curry with popadums and lime pickle, mmmmm spicy! Wednesday, marmite for breakfast (fingers this time, I like to vary my diet!) and for tea, a large white flat fish, not sure of the name but it was succulent and hit the spot, Thursday, missed my marmite and had a few tomatoes instead, for tea lamb chops and chips with salad! This morning I had......wait for it.....marmite! All in all, regular and consistent, no problems with the pipes!

In my existing waste pipe system, all runs well with no back ups or blocks but, it runs through the nextdoors garden and they want to build so I have to move it! The new run is shorter with the same amount of bends (1)! It's in 125mm dia pvc tube (or pipe, depending on your persuasion) and it runs due west for aproximatly 10m then abruptly changes direction to due south and 10m later joins the main system for the town!

The main syslem is 77cm under ground, and my pipes (or tubes) start at 10cm under ground!

If you want more info, just ask!

tube and pipe are 2 different things regardless of my persuasion.

I would call it a pipe ie, waste pipe, but here in Spain it is a tubo, Spanish for tube! Strange world!

go figure. I'm still trying to figure out why I have a 12" ruler.

Measuring device that is, not a small king.

Here in the states tube refers to a hollow piece of material measured by it's OD whereas pipe is measured by it's ID.

This is a bit misleading as many would argue that to have accurate flow rates and or volumes monitored; a pipe (which is categorized as a vessel) would be more logical than a tube (which is considered as structural). The control feature on tubing is wall thickness for accurate content/flow analysis as well as a tightly controlled OD dim for precision joining/mating.

cr3

Here in the UK I would run the pipe at 1 in 80 to an inspection chamber, then out of that in the new direction to another inspection chamber on the edge of your property just before it falls at a steeper angle into the town sewer

Check out the Blog entry "New Wave Tech Digs Indiana Sewer" where they call out a 0.25% grade on a large project. My dad (retired industrial engineer having worked on waste management projects) said the most common mistake is to make the slope too steep on horizontal runs where the fluids drain away too easily leaving the solids in place. A more gentle slope allows the fluids to float or carry away the solids. He advised me for household plumbing to use 1/4:12 or a 2% grade or 1.2 degrees. However, as with all the advice, I would recommend you contact your local governing agency responsible for construction permits/approvals and find out what the standards are for your area. They may have to approve your work anyways. Better to know up front the requirements for your job.

A good rule of thumb is 1/4" per foot . . . oh wait, all you blighters are on the wrong side of the "pond". I better convert my dimensions!

US codes will usually require 2% slope (1cm per 50cm run) for 100mm and smaller pipe, and allow 1% slope (1cm per 100cm run) over 100mm pipe. Slope is set to maintain sufficient flow velocity to carry any solids that are mixed in with the water, which is usually 2 to 3 feet per second. Our code books will have tables showing expected pipe flow capacity based on various slopes.

For sewer lines I was always taught (and have used) 1/4" drop for 12" of run. Or 1:48, round to 1:50. By some magic of gravity and the surface tension of water that keeps the "solids" moving. If you can't manage that then a 45 degree drop or steeper is required.

That doesn't seem to jive with the 1:100 number I've heard, so I could make some comment about American's ... never mind.

Oh, as an American I would expect that if your sewer line is running through your neighbor's garden that there must have been some sort of agreement in the deed to the property or a right-of-way granted for the sewer line. So I would hire a lawyer and make them either pay to have it moved or build around it! How nutty is that?

Ask your neighbor what they are planning on growing in the garden. If it is going to be non-food plants, cut the pipe and let if flow into the garden. They will have the biggest petunias in the neighborhood!

Also (to add SOME value to this post) as a sewer system design engineer, we used 1/4" per foot as the optimum slope. 1/8" per foot is ok for larger pipes with greater flow and 3/4" per foot is the maximum. If the natural grade was greater that that, we added drop manholes to let the water free fall in the manhole to lose head.

Each state and county has different codes .. best to call planning and zoning .... or whatever they call it to remain in code .... never hurts to be safe ... :)