Pitch of a Pipe

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Anonymous Poster	Pitch of a Pipe 11/06/2007 12:51 AM
	need to hook up a 4" PVC pipe to a holding tank . Will come out of the basement wall and run to the tank . Depth of pipe will be just about at the frost line in a cold winter . Need to know what the pitch ought to be on the pipe . Thought it was 1/4" per foot , but a friend suggested holding that pitch inside the building and a more severe one on the outside going from the house to the tank . Length outside is about 16 feet with two 45 deg elbows . The thought was that the pitch was needed inside to float the solids with a more rapid decent on the outside to try to keep the pipe without any standing fluids that could freeze it extremely cold weather . (cold enough to get the frost line down to the pipe level . Question is: what pipe pitch is needed , or where can I locate the information on the net ? Thanks .
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PWSlack Guru Join Date: Jan 2007 Location: In the bothy, 7 chains down the line from Dodman's Lane level crossing, in the nation formerly known as Great Britain. Kettle's on. Posts: 32175 Good Answers: 839	#1 Re: pitch of a pipe 11/06/2007 5:21 AM
	Underground 4" (100mm) soil pipe is run at 1 in 120 in the UK. The inside of plastic pipe used for this duty is quite smooth, for obvious reasons. Shallower gradients run the risk of incurring more frequent blockages. The correct sizing and number of rodding points is an important consideration. Almost every installation will require inspection and approval from the local authority's Building Regulations inspector before back-filling. One solution to a shallow pipe run issue is to install a macerator at the point where solids are produced. Most macerators have a little 'lift' available and are suitable for discharge into 40mm diameter waste pipe. __________________ "Did you get my e-mail?" - "The biggest problem in communication is the illusion that it has taken place" - George Bernard Shaw, 1856
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Bill Guru Join Date: Dec 2005 Location: Clemson, South Carolina Posts: 1722 Good Answers: 18	#2 Re: Pitch of a Pipe 11/06/2007 10:53 AM
	Hope you have a sense of humor . . . The pitch of a pipe is a function of it's length. It took a while, but I think I finally found the answer at Wikipedia: "The particular length "eight feet" is based on the approximate length of an organ pipe sounding the pitch two octaves below middle C, the bottom note on an organ keyboard. This may be calculated as follows. Physics tells us that if a pipe is open at one end, as is true of organ pipes, its fundamental frequency F will be: F = V/2L. If V is assumed to be 1130 feet per second (the speed of sound at sea level, with temperature 70 degrees Fahrenheit), and the pipe length L is assumed to be eight feet, then the formula yields the value of 70.6 Hertz (Hz.; cycles per second). This is not far from the pitch of the C two octaves below 440 Hz., which (when concert pitch is set at A = 440 Hz.) is 65.4 Hz. The discrepancy may be related to historical differing definitions of the length of the foot." __________________ We have met the enemy and he is us . . . Walt Kelly
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Brave Sir Robin Guru Join Date: May 2007 Location: Annapolis, Maryland Posts: 7940 Good Answers: 458	#4 In reply to #2 Re: Pitch of a Pipe 11/07/2007 8:46 AM
	LOL Now . . . who wants to put their head down their to listen?
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Andy Germany Guru Join Date: Sep 2006 Location: Near Frankfurt am Main, Germany. 50.390866N, 8.884827E Posts: 17996 Good Answers: 200	#3 Re: Pitch of a Pipe 11/07/2007 4:17 AM
	Using the infos from other CR4 Bloggers and make sure that you insulate the pipe as with a bit of luck, the products that are going down so to speak, still be above freezing point and will stop the pipe from freezing up! I have just installed a Toilet with Macerator (?) in a place upstairs far away from any sewage connection. Everything is pumped (at high speed, sounds like a quiet aircraft loo!!) through a 32mm plastic pipe (Glued!). The unit I have will pump up to 50 meters high!! So it is working at least up to 5 Bar (Whats that? about 70lbs sq.inch or so I feel) approximately. Very effective.... The Loo just looks like a normal one, no big box behind it, all the equipment is inside the base/pedestal, it cost a bit more, but its optically perfect! __________________ "What others say about you reveals more about them, than it does you." Anon.
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indel Guru Join Date: Oct 2007 Location: Sour Lake, TX 30°08'59.68"N 94°19'42.81"W Posts: 675 Good Answers: 13	#11 In reply to #3 Re: Pitch of a Pipe 11/07/2007 9:38 PM
	A friend of mine worked in Saudi Arabia, he was in the oil engineering. Once he was asked if can design a system comprising a powerful pump. The idea was to throw a jet of water, vertically, at such a height that the water would not come back, but will evaporate. I see that you are using the same idea, but with the contents of your toilet __________________ Bridge rule #1: Nobody is as good as he thinks about himself nor as dumb, as his partner thinks...
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Brave Sir Robin Guru Join Date: May 2007 Location: Annapolis, Maryland Posts: 7940 Good Answers: 458	#5 Re: Pitch of a Pipe 11/07/2007 8:55 AM
	Depending on the environmental conditions, I would suspect that the latent heat in the waste discharge is enough to keep the pipe from freezing as long as you are near the frost line. Also depends on the frequency of use, i.e. heat transfer to the pipe. It would be best to consult with your local plumbing codes to be in compliance with their requirements (even if you are not pulling a permit ) 1/4 -- 12 is a commonly used pitch for DWV of 4 inches or less.
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Anonymous Poster	#6 Re: Pitch of a Pipe 11/07/2007 9:38 AM
	A 4" pipe can be graded as low as 1/8" per foot grade. Also the heat generated by the bacteria in your septic tank will keep the pipe from freezing. It is true that inside the house minimal grade is acceptable but on the outside of the house it is not uncommon to grade the pipe at a steeper grade. As it states 1/8" minimum grade. Canadian code.
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ccoop610 Power-User Join Date: Nov 2005 Posts: 101 Good Answers: 9	#7 Re: Pitch of a Pipe 11/07/2007 10:13 AM
	Just a smattering of answers. The New York Department of Health states that any 4-inch diameter pipe containing solids shall be pitched at a minimum slope of 1/4 inch per foot. If the flow is composed of effluent only, then the minimum pitch is 1/8 inch per foot. The International plumbing code states that a 4-inch diameter pipe sloped at 1/8 inch per foot is limited to 180 fixture units. You ask what the heck is a fixture unit. For simplicity sake, assuming that your toilets are limited to 1.6 gallons per flush, it would take about 45 toilets all connected to that 4-inch pipe to equal 180 fixture units. You are okay capacity wise. But I would stick with 1/4 inch per foot if there are solids. The slope of 1/8 inch per foot translates to about 1 percent or 1 vertical to 100 foot horizontal. The slope of 1/4 inch per foot translates to about 2 percent or about 2 vertical to about 100 horizontal. Incidently, most of the time solids do not flow. They sort of tumble along until they decompose. A steeper slope (1/4 inch per foot) would definitely help the transportation process. Septic system piping is always installed above the frost line in northern areas. There is almost never a problem with it freezing because of the heat of the material that is flowing. Perhaps if you left your house was unihabited for the winter, there might be a problem. But as long as there is regular flow through the system, there should not be an issue.
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Anonymous Poster	#8 In reply to #7 Re: Pitch of a Pipe 11/07/2007 2:51 PM
	Heat of the material,that is flowing..............has to be one of the best I have seen in awhile. Congrats
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wgh71 Power-User Join Date: Aug 2007 Location: Virginia Posts: 122	#9 Re: Pitch of a Pipe 11/07/2007 7:20 PM
	Check your local zoning restrictions. Usually by county in the US. They will have a specific number for you. __________________ The major difference between a thing that might go wrong and a thing that cannot possibly go wrong is that when a thing that cannot possibly go wrong goes wrong it usually turns out to be impossible to get at or repair...Douglas Adams
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BlueAussieBoy Power-User Join Date: Sep 2006 Posts: 451 Good Answers: 16	#10 Re: Pitch of a Pipe 11/07/2007 8:47 PM
	I have found this post really interesting as I have never heard of the complication of freezing of an effluent pipe. As a kid growing up in Western Australia Dad use to get us up early if there was a frost. He didn't want us to miss it as it was such a rare event. Freezing effluent pipes sounds like another good reason to relocate. __________________ Make it so.
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Users who posted comments:

Andy Germany (1); Anonymous Poster (2); Bill (1); BlueAussieBoy (1); Brave Sir Robin (2); ccoop610 (1); indel (1); PWSlack (1); wgh71 (1)

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