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How to Connect Waste Pipes from Toilets on Several Levels

04/27/2016 2:03 AM

I'm designing my own future house, which will have toilets on three levels, and of course I want to consolidate the waste pipes into a single septic tank.

The question is, won't the head from the waste of the upper floor bathroom cause toilets in the lower floors to back up? How is this prevented in multistory buildings?

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#1

Re: How to connect waste pipes from toilets on several levels

04/27/2016 2:57 AM

Not sure what you mean by "backing up" but gravity should help you clearing the pipe.

Make sure you have a p-trap for your waste pipes.

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#22
In reply to #1

Re: How to connect waste pipes from toilets on several levels

04/28/2016 12:17 PM

The toilet has the trap built in, don't add another trap. - JHF

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#25
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Re: How to connect waste pipes from toilets on several levels

04/28/2016 9:33 PM

Sure, but all other waste pipes better have one!

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#2

Re: How to connect waste pipes from toilets on several levels

04/27/2016 3:26 AM

By searching on "multi story plumbing" you can get many diagrams and descriptions, better than words alone can give. Watch for slope requirements, predominant usage of 45-deg rather than 90-deg fittings, necessity of vents and cleanouts, etc. Check and follow local/regional regulations.

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#3

Re: How to connect waste pipes from toilets on several levels

04/27/2016 3:47 AM

Normal solution (in UK) is one main vertical soil pipe. The waste from each floor runs at a slight angle into the vertical pipe which is always empty except (as it is vertical) thus no chance of back up. The vertical pip also extends up to above the level of the eaves to provide a vent for noxious gasses and to prevent any pressure related problems.
Del

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#4
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Re: How to connect waste pipes from toilets on several levels

04/27/2016 5:57 AM

That's the part that I was missing. The waste pipes are not full of waste all the time - it comes down in slugs and moves on to the septic tank or sewage connection.

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#23
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Re: How to connect waste pipes from toilets on several levels

04/28/2016 6:34 PM

Actually the term "Slugs" is misleading. The solid parts or semi-solids are extremely dispersed in the liquid(s) by the time the mass gets to the drain/vent pipe,

First it is mixed with water in the bowl. There, depending upon its firmness (soft or diuretic to the solid or constipated range) the 1.6 gallons/flush of water will dilute and soften it somewhat. Next it must pass through a 2" clearance trap in the base of the bowl, about the size of a tennis ball The flow then goes into a 3" pipe (normally and PVC/ABS and (3" or 4" nominal size if the installation is less than 30 years old or so) to the waste/vent pipe. A full cross section of the pipe will seldom become clogged since the largest mass going through the pipe has a maximum diameter of 2" and it is proceeding through a 3" or 4" pipe that is vertical or pitched in the direction of flow. This pitch is a minimum of 1/4" per foot. When the mixture reaches the exit of the structure it must pass through another trap, usually 4" or larger. By the time it gets to this exit point it usually has the consistence of potato soup or thinner.

To field research this process if you live in a area with municipal sewers simple go out to the street and pop off a sewer man-hole cover. Always take a flashlight to facilitate light in the bottom of the piping so you can see. Also it is easier to lift the man-hole cover if you use a man-hole cover hook. There you can observe the mass flowing out as liquids or slight slurry. If you have a septic system pop the lid on the cesspool. take a rod and move the mass slightly so you can see the contents below any accumulation on the top.

I don't recommend opening up the trap in the house since it would be an excellent opportunity for someone to "get even" with you. The materials within can sometimes be quite odoriferous!

In summation, poop flows as a liquid or flexible mass, not rigid or unbreakable slugs. If you ever "dip honey," pay close attention to what you are dipping.

Good Luck, Old Salt

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#24
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Re: How to connect waste pipes from toilets on several levels

04/28/2016 7:25 PM

Sections of liquid surrounded by vapor or gas are called slugs, especially if they fill the cross-section of the pipe.

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#27
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Re: How to connect waste pipes from toilets on several levels

04/29/2016 1:03 AM

Perhaps different names for the same thing depending upon which trade/profession is describing it. Some engineering disciplines may call it a "slug" but the honey dippers call it a "glob of stuff".

It will be very difficult to fill the cross-section of at least a 3" pipe that is vertical or near horizontal pitched at 1/4" per foot. 1.6 gal/flush at a minimum of 5 seconds, assuming the higher rate of a "power flush" type toilet calculates out to roughly a quart/second of liquid/solids through the pipe. Also with ABS/PVC pipe the inner walls are much smoother than the old cast iron pipe thus facilitating a higher rate of flow and less chance of cross-section filling.

Remember two things about drain piping and sewer flow:" sh_t flows down hill but explodes uphill." Old Salt's principle of errant management.

During droughts where water is extremely valuable and usage must be kept at a minimum: "If it is yellow let it mellow, if it is brown flush it down."

Good Luck, Old Salt

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#26
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Re: How to connect waste pipes from toilets on several levels

04/29/2016 12:48 AM

In my office we use this chart to communicate to each other just how nicely the day is progressing or the quality of the client that we are dealing with without any of the public being any the wiser.

It just may be useful here as well.

Isn't life great being technical?

BAB

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#12
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Re: How to connect waste pipes from toilets on several levels

04/27/2016 5:20 PM

That's 'normal' here in the Colonies as well.

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#5

Re: How to Connect Waste Pipes from Toilets on Several Levels

04/27/2016 7:01 AM
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#6
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Re: How to Connect Waste Pipes from Toilets on Several Levels

04/27/2016 7:36 AM

Exactly what I'm afraid of!

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#7

Re: How to Connect Waste Pipes from Toilets on Several Levels

04/27/2016 10:02 AM

That's why the professions of the Architect and the Building Designer are held in such high regard. These sorts of people already know all this stuff, are familiar with local codes, and can do a better job that results eventually in less money being spent. It is a false economy not to involve them.

  • In the UK, one of the Buildings Control Officers from the local authority will be taking a detailed interest in the design and the development of the building during the construction phase. Anything that is not right will need to be put right at this time, with time and expense implications. Having a proper building design, compliant with local regulations, in front of them and "approved for construction" before construction starts will be found to be the smoothest approach to getting the building completed.
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#9
In reply to #7

Re: How to Connect Waste Pipes from Toilets on Several Levels

04/27/2016 10:22 AM

I'm in the Philippines. Even when I do hire "experts" - like for the structure of the house - it's very good to know enough to check their work. This will be my fourth (and last) move within this country, and all the houses I have lived in so far had defective plumbing. Mostly it was just bad workmanship, but the house I'm living in now has one toilet that must always be flushed twice.

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#14
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Re: How to Connect Waste Pipes from Toilets on Several Levels

04/27/2016 11:16 PM

I live a little north of you and experienced a similar flushing problem which was due the vent not being adequate. (The spec was correct but the builder took shortcuts when backs were turned - a common problem here).

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#19
In reply to #14

Re: How to Connect Waste Pipes from Toilets on Several Levels

04/28/2016 6:01 AM

I will be living on site and ordering the materials, so nobody's going to pull that on me.

I am curious: is it necessary to extend the waste vent at the full diameter of the waste pipe up to the roof, or is a smaller diameter possible?

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#8

Re: How to Connect Waste Pipes from Toilets on Several Levels

04/27/2016 10:15 AM
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#10
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Re: How to Connect Waste Pipes from Toilets on Several Levels

04/27/2016 10:27 AM

Thank you - this is very useful.

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#11
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Re: How to Connect Waste Pipes from Toilets on Several Levels

04/27/2016 10:45 AM
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#13
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Re: How to Connect Waste Pipes from Toilets on Several Levels

04/27/2016 10:30 PM

Very useful...details of the fittings used as well as their hookup.

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#15
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Re: How to Connect Waste Pipes from Toilets on Several Levels

04/27/2016 11:35 PM

Piolenc,

As you look at the many good drawings, you will notice that they all allow both gas and liquid/solid mix to move simultaneously. When you flush the toilet a significant amount of liquid must move down the pipe. As it does so, gas already in the pipe must get out of the way and then come back in after the liquid has moved by. The upward running vent connections allow this to happen and also take any odors caused by bacteria or foods to get outside.

--JMM

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#16

Re: How to Connect Waste Pipes from Toilets on Several Levels

04/27/2016 11:45 PM

My Asian plumbing experience says you can never have to many inspection points or ports that you can access to unblock drains and sewers. The additional cost is minimal and the time and convenience saved (is there a pun there somewhere) is well worth while. That is drainage covered.

On the water supply side, a small header tank is also a good idea. Some where about 2000 - 5000 litres. (1000 imperial gallons) This needs to be set high so that it provides a constant head pressure and a buffer for those times when the main water supply is not available.

BAB

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#17
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Re: How to Connect Waste Pipes from Toilets on Several Levels

04/28/2016 12:33 AM

Your thinking parallels mine.

I remember, from managing a small apartment building in the States, that there are never enough cleanouts.

And the need for decent water pressure here is obvious: I intend to have a header tank (probably no more than 1 cu. m) on top of each of the steel columns holding up the house (the columns extend through the roof about 2.5 meters, enough head for the downstairs and basement bathrooms, maybe not enough for the guest bathroom on the 2nd floor). The main water supply will be in the basement, and pumped up to each header tank as needed.

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#21
In reply to #16

Re: How to Connect Waste Pipes from Toilets on Several Levels

04/28/2016 10:46 AM

"My Asian plumbing experience says you can never have to many inspection points or ports that you can access to unblock drains and sewers. The additional cost is minimal and the time and convenience saved (is there a pun there somewhere) is well worth while. That is drainage covered."

That's what I was thinking when I redid the poorly designed sink drain in my house, I used 'sanitary Tees(1)' with an 'inspection plug' instead of elbowes, and replaced the 90 degree-90 degree 'S curve' where the pipe jogged around the edge of the basement wall with a 45-45 'S curve. The water drains fast ans smooth, and if there is a clog, with all the inspection plugs, I could 'snake' the pipes with a solid iron bar.

Notes:

  1. The Sanitary Tee has a straight section, and the 'third leg' of the Tee is build like an elbow, directing the flow of material. Think of it as having a 'top,' 'bottom,' and 'side' opening. material entering the Top flows right to the Bottom, material entering from the side is deflected so it flows to the Bottom instead of splashing up to the Top. This even works if the Top and Bottom are aimed to the left and right, and the Side points up(2).
  2. If you install the Tee on a slope, so the Bottom is higher than the Top, gravity will take over and make the material exit the Top. but this would be called "Installing the Tee wrong."
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#18

Re: How to Connect Waste Pipes from Toilets on Several Levels

04/28/2016 5:29 AM

You need to note that the system should NEVER be hydraulic. That is, the wastewater flowing in the pipes should never be a complete cross section of the pipe, otherwise you will get syphoning from other connected fixtures.

Proper design means that the water cross section in the pipes is typically less that 15% of the pipe cross section. This means that when other fixtures are used (flushed) at the same time, there is still available cross section for the air to move past the flowing liquid.

Similar ratio applies for the sewer mains in the street.

This is achieved by following the local design guidelines and codes.

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#20
In reply to #18

Re: How to Connect Waste Pipes from Toilets on Several Levels

04/28/2016 6:05 AM

I'm going to need some firmer basis of calculation that "local guidelines." But just knowing that this is a potential problem will be helpful. Presumably, when two or more waste lines are consolidated or emptied into a single one, that single one must have a bigger diameter...

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