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  1. #1
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    Default Plumbing experts-? traps

    Something I have always wondered about, what is the advantage, other than code requirements, to having a trap on each sink, tub, shower, etc. over havening a single trap on the waste main?
    Jack
    Be sure you live your life, because you are a long time dead.-Scottish Proverb

  2. #2
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    Default Re: Plumbing experts-? traps

    I think it has something to do with dropping too far can lead to the water outrunning the waste to the trap...... allowing the waste to collect in the trap and not being washed through the trap creating a blockage or hastening a blockage in the trap.


    Just a guess.
    "" an ounce of perception -- a pound of obscure "
    - Rush

  3. #3

    Lightbulb Re: Plumbing experts-? traps

    If you have seperate traps and one of the fixtures clogs the other fixture would work.One trap could clog faster too.

  4. #4
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    Default Re: Plumbing experts-? traps

    Especially when the trap would be after the toilets.

    There wouldn't be enough water to wash the 3 inch trap from smaller fixtures like a bath room sink.


    Still just guessing.
    "" an ounce of perception -- a pound of obscure "
    - Rush

  5. #5
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    Default Re: Plumbing experts-? traps

    Not to mention that fumes from every fixture, toilets included would waft up to all the other drains. It's also easy to remove a p trap to fix or unclog without effecting any other drain in the house.

  6. #6
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    Default Re: Plumbing experts-? traps

    Quote Originally Posted by JLMCDANIEL View Post
    Something I have always wondered about, what is the advantage, other than code requirements, to having a trap on each sink, tub, shower, etc. over havening a single trap on the waste main?
    Jack
    you answer a lot of drain plumbing questions in your posts and you ask this? i not a plumber expert but we learnt about this in junior high science health and history classes! the bacteria viruses and gasses in the sewer system can make you sick or kill you and some of the gasses can burn or explode. my kids in 3rd and 5th grade are already learning about this.

    traps prevent air passage and keep the air from the dirty plumbing directed to the vents when waste flows thru them. fluids cant go in easily unless air can go out. gravity drives the waste plumbing. we learnt about this in pactical lab with a glass straw called a pipet how the vacuum and water tension overcame the gravity on the fluid in the pipet when we held finger on the top of it as we drew it from the beaker of fluid and that it could fall down when we took finger off and looked at finger and saw how it was puffed out in center of a ring shape. its the same reason catsup wont flow right away if you uncap a new glass bottle and turn it upside down and people bang on the end to make it splatter out after air gets in or stuff a knife in it to make an air vent into the catsup then it will flow out and if you hold it sideways and tap the lower side of the neck it will flow faster because air can get into the bottle easier at the top if it is sideways.

    keeps things balanced otherwise plumbing would burp into the sink and contaminate it and the air.

    the sewer and waste pipes start out neutral pressure, gravity force on weight of waste causes a bit of positive pressure the trap seal water offers resistance to the positive pressure from waste in other pipes the pressure air releasing will travel vent path least resistance up the clear vents if not to strong. air movement from pipes and sewer to vent causes slight negative pressure behind the waste slug. supposed to avoid to much negative or vacuum pressure in plumbing to its supposed to work on gravity and balanced pressure not suction like a vacuum cleaner the sewer isnt a suction mabe lifter pumps in the stream but thats it. not like a suction system like on a plane toilet or a ship.

    you see this negative and positive pressure slugs and equalizing problems and gravity effects easier when taller waste systems like in apartment buildings with three or four floors and high ceilings because of the increasing velocity (accelleration) when things fall (gravity). at one second 16 feet traveled to fall at 2 seconds aprox 64 feet aprox. acceleration due to earth gravity was something like 32 feet per second squared when rounded off. my 5th grader is learning about Newton now but these days they do it all in metric so i might have bungled the numbers i am no plumber and not a math wiz, but then it gets slowed down by friction drag atmosphere in the pipes and stuff.

    bottom line is if the fixture is above the sewer, without a trap for every individual fixture, you turn a untrapped fixture into another vent stack for the sewer itself and the drains. if there is enough waste stream from higher up fixtures and not right venting you can get burping sewer fountains at the lower fixtures contamining the fresh water fixtures. your sewer venting will take the path of least distance and resistance to free air equalization you want this to be the main stack vent if fixture is untrapped or unsealed and is closer and lower than your main stack vent that will be the direction the air will go. that is why we trap every non mechanically drained fixture indoors.
    Last edited by Blue RidgeParkway; 09-02-2008 at 02:05 PM.

  7. #7
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    Default Re: Plumbing experts-? traps

    Quote Originally Posted by Blue RidgeParkway View Post
    you answer a lot of drain plumbing questions in your posts and you ask this? i not a plumber expert but we learnt about this in junior high science health and history classes! the bacteria viruses and gasses in the sewer system can make you sick or kill you and some of the gasses can burn or explode. my kids in 3rd and 5th grade are already learning about this.

    traps prevent air passage and keep the air from the dirty plumbing directed to the vents when waste flows thru them. fluids cant go in easily unless air can go out. gravity drives the waste plumbing. we learnt about this in pactical lab with a glass straw called a pipet how the vacuum and water tension overcame the gravity on the fluid in the pipet when we held finger on the top of it as we drew it from the beaker of fluid and that it could fall down when we took finger off and looked at finger and saw how it was puffed out in center of a ring shape. its the same reason catsup wont flow right away if you uncap a new glass bottle and turn it upside down and people bang on the end to make it splatter out after air gets in or stuff a knife in it to make an air vent into the catsup then it will flow out and if you hold it sideways and tap the lower side of the neck it will flow faster because air can get into the bottle easier at the top if it is sideways.

    keeps things balanced otherwise plumbing would burp into the sink and contaminate it and the air.

    the sewer and waste pipes start out neutral pressure, gravity force on weight of waste causes a bit of positive pressure the trap seal water offers resistance to the positive pressure from waste in other pipes the pressure air releasing will travel vent path least resistance up the clear vents if not to strong. air movement from pipes and sewer to vent causes slight negative pressure behind the waste slug. supposed to avoid to much negative or vacuum pressure in plumbing to its supposed to work on gravity and balanced pressure not suction like a vacuum cleaner the sewer isnt a suction mabe lifter pumps in the stream but thats it. not like a suction system like on a plane toilet or a ship.

    you see this negative and positive pressure slugs and equalizing problems and gravity effects easier when taller waste systems like in apartment buildings with three or four floors and high ceilings because of the increasing velocity (accelleration) when things fall (gravity). at one second 16 feet traveled to fall at 2 seconds aprox 64 feet aprox. acceleration due to earth gravity was something like 32 feet per second squared when rounded off. my 5th grader is learning about Newton now but these days they do it all in metric so i might have bungled the numbers i am no plumber and not a math wiz, but then it gets slowed down by friction drag atmosphere in the pipes and stuff.

    bottom line is if the fixture is above the sewer, without a trap for every individual fixture, you turn a untrapped fixture into another vent stack for the sewer itself and the drains. if there is enough waste stream from higher up fixtures and not right venting you can get burping sewer fountains at the lower fixtures contamining the fresh water fixtures. your sewer venting will take the path of least distance and resistance to free air equalization you want this to be the main stack vent if fixture is untrapped or unsealed and is closer and lower than your main stack vent that will be the direction the air will go. that is why we trap every non mechanically drained fixture indoors.
    I guess it's kids stuff.

    Do they even make a 3 inch P trap for homes?

  8. #8
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    Default Re: Plumbing experts-? traps

    A 4" trap would hold less than gal, so any fixture would supply enough water the flush or refill the trap.

    If the main trap has water in it that would stop the sewer gas from entering the line so there would be no sewer gas coming out of the fixtures.

    If the main line gets clogged and you flush an upstairs toilet you can still get toilet water in a downstairs sink even with a trap.

    Blue RidgeParkway
    The function of the traps and the function of the vents are two different things telling of your grade school education in fluid dynamics still doesn't answer the question.

    Is gravity the main reason? Possibly.
    Jack
    Be sure you live your life, because you are a long time dead.-Scottish Proverb

  9. #9
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    Default Re: Plumbing experts-? traps

    First, JCLMCDANIAL LOL
    Second, blue ridge parkway:
    my impersonation ahem : blah blah blah words words words.
    The reason is that the people that write the code say so. I suppose it could be legionella spores or other waste bourne microbes but who knows? However MAC you're wrong about one thing for sure no house fixture has enough volume to scour a house trap. There is just too much fluid mass. The surface tension of the fluid and the friction of the pipe would just flow through and that is not what the code writers want if you see where sizing fixture traps is discussed. Other wise plumbers would do the absolute minimum were it allowed.

  10. #10
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    Default Re: Plumbing experts-? traps

    i.m.plummin
    You are correct most fixtures will not scrub a whole house trap, however the point was that it takes very little water to keep the trap filled. A toilet flush would probably be needed to scrub the trap. I don't think that would be a problem unless there is a garbage grinder. Code is set not only for safety but to sell products and labor and if possible to make it as difficult for DIYers as possible. And to keep the pros going back for additional training.

    Jack
    Be sure you live your life, because you are a long time dead.-Scottish Proverb

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