Jan 30, 2007, 10:52 AM
Post #15 of 30
Bubba, a vented plumbing system means that every fixture has a continuation of the drainpipes up through the roof and open to the atmosphere. Lets say it is the pipe that drains a sink, instead of using a 90 ° elbow at the sink to connect the sink trap, a drainage tee is used, the pipe then continues up 9 to 12 inches above the roof.
Generally, every fixture must have it’s own separate vent. They can be connected together in the wall and a single pipe may be used to vent them all through the roof, this is called re-venting. Venting a fixture when the drain piping is all under the floor, such as a toilet, sometimes requires that the vent be connected to the horizontal drainpipe, when there is not enough room to stack a tee in the vertical riser pipe to the fixture. If a fixture is vented in that manner, the vent must be connected above the centerline of the horizontal drainpipe, the top of the pipe is the preferred connection point.
Sometimes, the drain for one fixture is used as the vent for a lower fixture in the building. That is called a “wet vent”. Wet vents work very well usually, but sometimes they are a disastrous mistake. For that reason, most plumbing codes prohibit the use of wet venting altogether, except in The State of Texas, where the codes actually encourage wet venting. At one time, I held a Master Plumbers license (plumbing contractor) in Texas.
Since venting an existing toilet down here would require the breaking up of the concrete floor, it would probably be best to not attempt to add a new vent to an existing toilet, but to depend on the other new vents on the other fixtures to act as wet vents for the toilet. There are no gaurantees, but it will probably work OK.
To get a plumbing contractor’s license in most if not all states, you must pass a very comprehensive test to prove that you are qualified to do plumbing work. It is a public health and safety issue. If you don’t know what you are doing, you can poison a whole town, or cause great damage by gas or water heater explosions, etc.
Vents prevent pressure from building up in front of liquids bring drained, or a partial vacuum from forming behind water draining, that will slow the rate that the wastewater will drain. The lack of vents is the reason that many toilets down here do not flush efficiently enough for paper to go down the drain. Vents also dissipate the foul odor of sewer gas. It’s pretty simple really.
Sewer gas is always noxious, sometimes toxic, sometimes flammable, and sometimes inflammable. Flammable and inflammable are not synonyms. A flammable substance will burn if it is ignited. An inflammable substance is an unstable substance that may self-ignite, in other words; it may explode. You don’t want sewer gas in your house.
Traps are used to prevent sewer gas from entering the house, but they exacerbate the problems in a non-vented plumbing system. The traps used here in Mexico often depend on a mechanical part to hold the gas back; usually those parts look something like an inverted cup or bowl. Those parts are often missing, that is probably why you can smell the gas in your shower.
Traps that depend on any mechanical part to function are illegal to use in every jurisdiction I have ever worked in, in the USA. There are some special use exceptions, but the only types of traps usually approved for use up there are P-traps, drum traps, and sometimes S-traps. They depend on the water they hold in them to seal the plumbing system.
You might want to try a Google search for “plumbing codes”. Some of the codebooks have illustrations in them, if you can find one that does; it will be very helpful to see how a properly installed plumbing system looks.
I discarded my last codebook when we moved to Mexico. I wish I hadn’t done that now. It had been many years since I worked as a plumber; I had changed my specialty in the pipe trades to pipefiitter, with a specialization as a process control technician. After several years of education and experience working as a plumber, I have forgotten none of it.
A big part of the problem with getting a proper plumbing system installed in Mexico is that I have never seen any drainage fittings in any hardware store or plumbing wholesale house anywhere in Mexico. That includes the much-vaunted Home Depot stores.
Drainage fittings are very different than water fittings. They have and arc, or “sweep” built into them in the direction of the water flow. That is important. There are also many different degrees of drainage elbows, which I have never seen down here. There are 11 1/4°, 22 ½°, 45°, 60°, 72° and of course 90° elbows which are often required, in a soil pipe system elbows are called “bends.” A soil pipe system is any drainage system that handles human waste.
The closest fittings that I have seen for use in drainage work here are wyes, and 45° elbows, that really puts a limit on connecting a pipe to another when they are at unusual angles to one another. I think that explains why the blockhead “plumbers” down here build and use those registros to connect pipes in the patio.
The registros by their very nature are an insanitary condition. Yes, insanitary is a word.
Installing a vented plumbing system in a home in Mexico is probably beyond the experience of most, if not all homebuilders here. It would require a great deal of pre-planning, and a massive change in construction methods to accommodate the pipes in the walls. To retrofit an existing house with plumbing vents would require a massive amount of chipping away of the masonry walls, and a weakening of the structural bond beams where the vents will need to pass through them.
If the bathrooms, and other plumbing fixtures are located at an outside wall, a more practical, although uglier solution would be to locate the vent pipes on the outside surface of the wall, and extend them above the roof line. The pipes will be visible and not attractive. I have done this on older homes in Napa when a second bathroom was added.
Good luck with your project, Rex
"The supreme happiness of life is the conviction that we are loved" - Victor Hugo
(This post was edited by RexC on Jan 30, 2007, 11:08 AM)