How a Plumbing Trap Can Lose Water



Watch the full episode: http://www.thisoldhouse.com/toh/tv/ask-toh/video/0,,21002944,00.html Ask This Old House plumbing and heating expert Richard …

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49 thoughts on “How a Plumbing Trap Can Lose Water”

  1. Finally got a straight answer to why S traps are bad. Thank You! I just bought a 1970 cottage here in Ontario Canada and it has S traps that I was told should be replaced cause they dry out fast. Couldn't get my head around why they would dry out faster than a P trap.. now I know 🙂

  2. Boy, your plumbing is so primitive. You would never get a 1” and a half pipe siphon out a 4” trap! And the toilet pan in your demo is a siphonic pan as this has a built in air brake you’d never pull the trap. You can’t even successfully plunge them!!1

  3. I thought he said there were about 7 ways of losing traps seals. I only counted 6. Also, I see mention of 8, which I'll have to go look for now. I believe partial blockage in a drainage line can slow the flow down to a point where a toilet trap can't refill itself completely.

  4. `Don't neglect the vent outlet. If it's under a tree, over time, spent leaves can clog up the trap. Solution: A screen over the top of the vent, using a zip tie to fasten it.

  5. Mechanical vents should never be used. They only last so many years and will need to be changed and you wont know it until your house smells like sewer gas. Add in the fact that some bury them in walls or other hiding places and don't disclose to the owner or if the past owner knows they never pass it along to a new owner they should be taken off the market.

  6. Any different, using PVC trap / pipe between 2" or 1 1/2" , which one to faster drain time ?
    I am using 1 1/2" trap now it took very slow to drain the full water from tub.

  7. Am a plumber 12 years already bout the toilet sewer gas will never go into house because of toilet fill valve if it's loses water the filler well put the water you adjusted it to if your filler valve don't work you will always hear water running tru your toilet drain waste of water higher water bill to pay

  8. A couple other issues I've run into many times in my 28 years of plumbing.
    1 – Distance from disharge to trap (each size pipe has one in the code book). Too far of a drop will simple have too much momentum and break the seal of the trap.
    2 – Wind. Not so rare in windy areas where guest bathrooms aren't often used. It's something that can greatly increase normal evaporation.

    If you have a seasonal home service, be sure they know to run water through all your plumbing fixtures during their bi-weekly or monthly check. Traps are essential for blocking out Methane. People hear sewer gases and think that means smelly gas. Traps help that as well, but Methane is odorless and in a large city with high methane, a trap with a broken seal can mean your family dies in their sleep.

    For Southern areas, such as Florida, and since many people have seasonal homes in FL, this issue is different. Methane is weak, or non-existent, but now you're most likely in bug land. I now live in SWFL and have educated countless home service companies on the importance of running water. The wind here is strong during season and there are all kinds of species of bugs traveling around in your vent system waiting for a way in. I actually don't speak from my plumbing experience on this one, but when I did work for my brother in law's pest control business in Naples, FL. Home owners didn't like coming home to a floor covered in huge palmetto bugs (American Cockroach).

    25 years of plumbing in the Boston area taught me well, but moving to FL opened my eyes to new issues I never saw up north. I do mostly commercial plumbing here but as mentioned, it was my pest control work that showed me the last issue and not plumbing.

  9. I really appreciate what this old house is trying to do but dear god trying to use their videos to study for a plumbing apprenticeship exam is like watching Barney to become a paleontologist.

  10. I been in my old house for 3 years and I can't figure out where these little tiny flying gnats are coming from.      I checking  the Basement sink I'm thinking they're coming up the drain when the water evaporates in my P trap  from lack of use?

  11. That toilet isn't plumbed according to code. You can't have another fixture line coming off of the toilet arm like that. There would have to be a vent between the 2" branch and the toilet arm.

  12. I run all my sinks, toilets, tubs and showers at least monthly. Never had any gas smell and seals, valves and flush mechanisms stay "lubricated" and resilient.

  13. I'm an old plumber. I don't think he mentioned the most obvious; trap failure. If a trap cracks or a joint fails, water will leak out. Some traps are below the floor like the tub or the shower. some may have frozen and burst. You wouldn't know it unless you smelled sewer gas.

  14. Sir I have a question I have bad odor coming out the shower I have I noticed that my house does not have a ventilation pipe. Can that be the broblem? And if so how can I fix this broblem. Thank you

  15. I work in the Building Trades as an HVAC guy in a commercial setting and they use now some type of watering system that keeps adding water to the traps in the buildings actually think it's code in some places now

  16. When I started the maintenance job at my current facility I got a whole week to organize the old maintenance shop and go over things with the temporary maintenance guy who is covering. I smelled something in the maintenance shop for about two days before I figured it out. They converted a bathroom and left the toilet and urinal in place and covered it up. Turns out I have to flush the toilet every few months and the smell goes away again

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