Ask Me Help Desk - Proper venting of drain lines

I am building a new home in Thailand (no frost). Thai plumbers don't understand venting, so I have tried to draw a drain and vent plan for them. I have two drain lines that merge just prior to entering a vented septic system.

On one line I have a shower, two sinks and a toilet. On the other I have a bath, one sink, and a toilet. My plan is to have a single 2" vent located at the upstream end of each drain line. Both vents will exit through the roof.

This should provide an upstream air source regardless of which fixture is in use, which is the purpose of venting as I understand it. Is this sufficient venting?

To vent your plumbing fixtures is always a good idea. Now it depends what Code you want to use to rough it in. I work under UPC. UPC mandates venting of each plumbing fixture in the house. Other Codes allow so called "wet venting." I will let other Experts in this forum to comment on wet venting.

If you draw and post a simple diagram of your layout, I will be more than glad to draw you my sketch showing placement of all vents - as per UPC - throughout you're the house.

Back to you / Milo

Quote:

Originally Posted by Milo Dolezal

To vent your plumbing fixtures is always a good idea. Now it depends what Code you want to use to rough it in. I work under UPC. UPC mandates venting of each plumbing fixture in the house. Other Codes allow so called "wet venting." I will let other Experts in this forum to comment on wet venting.

If you draw and post a simple diagram of your layout, I will be more than glad to draw you my sketch showing placement of all vents - as per UPC - throughout your the house.

Back to you / Milo

Thanks for the prompt response. However, I'm not really interested in what the codes say, UPC or otherwise. There are no codes here in Thailand--at least none that apply.

What I want to know is whether the vents will do what vents are supposed to do (prevent p-traps from being sucked dry). I've attached a simple diagram of what I'm planning. The arrows indicate the direction of water flow. Will 2" vents be adequate? Do you think additional vents will be required?

I'll answer your question, but then you MUST get me an authentic street recipe for thai chicken gra pow... promise?

Assuming you promised, your diagram won't work out... will lead to traps getting siphoned out!

Look at my diagram...

See that the toilets are coming off the main trunk line as the main branch (3" minimum) of each bathroom. Then the 2" sink drain comes off the 3" drain line (rolled above the center of the drain line) and picks up the shower drains as well as the sink drains.

These 2" vents piped in this way, WET VENT the toilet and showers using the sink vents...

You want to ad cleanouts wherever you can, too! Be sure to add PTRAPS to the sinks and the showers!

Questions? Let me know... and don't forget to get me that recipe, if possible as real thai recipes are hard to get over here!

Mark

Quote:

Originally Posted by massplumber2008

I'll answer your question, but then you MUST get me an authentic street recipe for thai chicken gra pow...promise??

Assuming you promised, your diagram won't work out...will lead to traps getting siphoned out!

Look at my diagram...

See that the toilets are coming off the main trunk line as the main branch (3" minimum) of each bathroom. Then the 2" sink drain comes off the 3" drain line (rolled above the center of the drain line) and picks up the shower drains as well as the sink drains.

These 2" vents piped in this way, WET VENT the toilet and showers using the sink vents...

You want to ad cleanouts wherever you can, too! Be sure to add PTRAPS to the sinks and the showers!

Questions? Let me know...and don't forget to get me that recipe, if possible as real thai recipes are hard to get over here!!

Mark

OK. One question. What is the reason for putting the vents at the sinks rather than the showers? Is it because of the differential in air pressure due to the height of the sinks? We will definitely be installing p-traps everywhere.

As for your recipe, I've never heard of chicken gra pow (in Thai that would be "gra pow gai"), but I'll ask my wife. If I can't get you that, can I substitute one of my favorites?

BTW--You do know that authentic Thai cuisine is VERY spicy? Also, a pestle and mortar should be used to crush and mix the spices.

I understand. But Code makes sure your plumbing system is built so it functions properly.

Now, regarding that chicken...

:)

Milo

In wet venting (where allowed), it is assumed that two fixtures will not operate at the same time, so if you follow waste water from any one fixture you can see that there is always a 2" vent contribution from the 2" sink drain/vent... keeps trap from siphoning and allowing sewer gasses into the home!

I know Thai is spicy (I also know it could kill me if I go too far!). I have heard of so many different variations on the name, "gra pow gai" (spicy basil and chicken? ) that I will definitely lean toward your interpretation over mine! I also cook a lot of different recipes, and believe it or not, own my own mortar and pestle! I even have most of the Thai sweet, sour, salty, and spicy ingredients!

Seriously, if you could come up with a real recipe from the area it would be tons of fun for me (and Milo)!

Glad to discuss more...

Quote:

Originally Posted by massplumber2008

In wet venting (where allowed), it is assumed that two fixtures will not operate at the same time, so if you follow waste water from any one fixture you can see that there is always a 2" vent contribution from the 2" sink drain/vent....keeps trap from siphoning and allowing sewer gasses into the home!

I know Thai is spicy (I also know it could kill me if I go too far!). I have heard of so many different variations on the name, "gra pow gai" (spicy basil and chicken??) that I will definitely lean toward your interpretation over mine!! I also cook alot of different recipes, and believe it or not, own my own mortar and pestle!! I even have most of the Thai sweet, sour, salty, and spicy ingredients!!

Seriously, if you could come up with a real recipe from the area it would be tons of fun for me (and Milo)!

Glad to discuss more...

I can provide the recipe, but I'm waiting on my wife. Please note, the wife says you will not get the results you want without "Thai" basil. Hopefully, you have a source. (yes, "gai" is the Thai word for chicken).

Regarding your description of wet venting and the fact the vent can be "seen" from any fixture, I thought I had accomplished that with the diagram I sent you? The vent coming off the shower would be available to any fixture on the same drain line. The shower will see the vent when the shower is in use, the sink(s) will see the vent when the sink(s) is in use, and the toilet will see the vent when the toilet is in use.

In short, I don't see any difference in functionality between my original plan and yours. What am I missing?

Ga Pow Gai

Chicken - 500g
Thai basil leaves - 2 cups
Thai chilies - 3 small (very spicy)
Garlic - 3 large cloves
Sugar - 1 tsp
Chicken boullion - 1 tsp (2 cubes)
Maggi - 1 tbsp
Oyster sauce - 1 1/2 tbsp
Soy sauce - 1 tbsp
Dark soy sauce - 1/2 tsp (for color)
Water - 3 tbsp
Red chilies - 2 tbsp (mild, sliced)
Vegetable oil - 2 tbsp

Slice chicken into thin strips approx 1 inch long.

Partially crush Thai chilies and garlic in mortar

Place oil in frying pan and heat on medium high flame. When hot, add partially crushed
Chilies and garlic and stir briefly. Add chicken, stir. Add water, sugar, chicken
Boullion, Maggi, oyster sauce, soy sauce, dark soy sauce. Stir fry until chicken is done.
Add Thai basil and red chilies, toss briefly, then remove from heat and serve.

Serve on bed of rice (jasmine) or with rice on the side.

Thank you for that recipe... really appreciate it!

In terms of what you drew and what I drew up, you need to understand that a sink drain cannot have an STRAP which is what you end up with if you don't install a vent at the sinks. Here, the trap will make an s-shape (goes into the floor) and the trap can get siphoned every time you run the sink... pulls on the water in the trap. A vent, with a PTRAP eliminates this and will not allow sewer gasses into the home!

Using the sink drain and vent to vent the other fixtures is how wet venting works as long as you install a PTRAP at the shower, and of course, your toilet has an integral trap.

That make more sense?

Quote:

Originally Posted by massplumber2008

Thank you for that recipe...really appreciate it!

In terms of what you drew and what I drew up, you need to understand that a sink drain cannot have an STRAP which is what you end up with if you don't install a vent at the sinks. Here, the trap will make an s-shape (goes into the floor) and the trap can get siphoned every time you run the sink...pulls on the water in the trap. A vent, with a PTRAP eliminates this and will not allow sewer gasses into the home!

Using the sink drain and vent to vent the other fixtures is how wet venting works as long as you install a PTRAP at the shower, and of course, your toilet has an integral trap.

That make more sense?

That does make sense. Actually, the reason I thought the vent would be better placed at the end of the drain line, by the shower, was to avoid the siphoning effect at the shower as well. I thought that as long as there was an open vent on the drain line UPSTREAM from the sink, it would still protect the sink. I don't see how a DOWNSTREAM vent will prevent siphoning at the shower.

You can ignore me at this point if you want. I'm just one of those people who likes to understand "why", not just how.

I hope you enjoy the ga pow gai! Thanks for your assistance. Much appreciated.

The why factor can only be understood with a good grasp on how, which mark has given you. For a complete understanding of how plumbing drain, waste, and vent works, you may need to study the subject for years and years like licensed plumber have to. Even then, some plumbers make it through and still don't have a full grasp on the correct modern day way of doing things. We can tell you the correct way of doing things to meet current codes in the U.S. but to try to get you to understand why could take more time than we will ever be able to put up here. The way you plan to do your job will most likely work to a certain extent, but we as licensed plumbers are telling you the way it will work best in regards to modern plumbing specs in the states. S-traps are illegal in the states and are easily siphoned. You would have an S-trap if you don't vent the lav. Now, all that being said, I think maybe you will be fine doing the job as you suggest, but use an AAV at the sink. Or, just let the plumbers do things the way they do them around there. We can't make you do anything, and nobody really can if there are no codes in your area. It really comes down to if you want it done safely, to modern codes applying to most of the civilized world, or you just want it done. Mark drew up the ideal install, but there are many options that vary from that, they would be much more involved than his diagram. You have to realize that you are on a plumbing page, so we will give plumbers advice. It hurts for us to say, sure it will work, but it isn't to code. Fact is (it hurts) but it will work to do it your way. Just wouldn't pass inspection here, you know? And in this day and age, and the fact that you know the plumbers there don't know anything about modern safe plumbing, why not take the advice given here by the pros? We have no intention of ignoring you at this point, just want to explain how to do things the way we know they work best at this point. Like I said, this is not something you learn overnight, so you either need to get really involved with plumbing codes, or take our advice. We have already put our time into learning and understanding this ever changing world of plumbing.

Quote:

Originally Posted by mygirlsdad77

The why factor can only be understood with a good grasp on how, which mark has given you. For a complete understanding of how plumbing drain, waste, and vent works, you may need to study the subject for years and years like licensed plumber have to. Even then, some plumbers make it through and still dont have a full grasp on the correct modern day way of doing things. We can tell you the correct way of doing things to meet current codes in the U.S. but to try to get you to understand why could take more time than we will ever be able to put up here. The way you plan to do your job will most likely work to a certain extent, but we as licensed plumbers are telling you the way it will work best in regards to modern plumbing specs in the states. S-traps are illegal in the states and are easily siphoned. You would have an S-trap if you dont vent the lav. Now, all that being said, I think maybe you will be fine doing the job as you suggest, but use an AAV at the sink. Or, just let the plumbers do things the way they do them around there. We can't make you do anything, and nobody really can if there are no codes in your area. It really comes down to if you want it done safely, to modern codes applying to most of the civilized world, or you just want it done. Mark drew up the ideal install, but there are many options that vary from that, they would be much more involved than his diagram. You have to realize that you are on a plumbing page, so we will give plumbers advice. It hurts for us to say, sure it will work, but it isnt to code. Fact is (it hurts) but it will work to do it your way. Just wouldnt pass inspection here, you know? And in this day and age, and the fact that you know the plumbers there dont know anything about modern safe plumbing, why not take the advice given here by the pros? We have no intention of ignoring you at this point, just want to explain how to do things the way we know they work best at this point. Like I said, this is not something you learn overnight, so you either need to get really involved with plumbing codes, or take our advice. We have already put our time into learning and understanding this ever changing world of plumbing.

You completely mistook my response. Saying "you can ignore me if you want" was my way of letting <massplumber> know that I knew I was asking a lot and I didn't expect him to offer a "why" explanation, though I would be deeply interested.

After staying up half the night pondering the difference between <massplumber>'s diagram and mine, I think I grok the "why". Here's how I understand it:

The reason there is no problem with the shower in <massplumber> diagram is that the PTRAP will not behave like an STRAP until the drain line falls below the P as it moves toward the septic system. As long as the shower is within a reasonable distance of the sinks, it will be vented properly.

I believe my original plan would also work. My plan was to have the PTRAPS for the sinks below the floor, just a tad lower than the shower PTRAP but higher than where the drain line joins the toilet (so as to maintain slope). In this situation, there would be no STRAP at the sinks, far as I can tell, and the vent at the shower would function just as well for the sinks.

Regarding your other comments on CODE. I respect code, but I also realize that codes in the U.S. are developed to be as general as possible (out of necessity). In specific cases they can be overkill. My comments about code were simply to inform any readers that I did not have to worry about code in Thailand, as there is none (nor are there inspectors). What I wanted was a "pragmatic" solution, not a legal one.

Lastly, I am curious. I like to know "why". I take every opportunity to understand the world around me and how it works. As for any slight that may have been felt, it was unintentional. As you yourself pointed out, many plumbers never really understand what they are doing. The same can be said for every profession. Here in Thailand, one of the other challenges I have is working with the electricians. I've never seen a Thai house that was actually grounded. Most houses only have 2-prong outlets. Polarity is sometimes switched. Etc. etc. etc.

Just so you know where I'm coming from:

I may not be an expert plumber (which is why I asked the question), or an expert electrician, but I have worked in construction. I also studied physics and electronics while in university (among several other sciences). So I'm not an idiot. In fact, I have over 20 years of education and have worked in more fields than most any 3 people put together have. I have lived and worked throughout the U.S. as well as several foreign countries (third world) In short, I am well educated and well experienced. I do not hesitate to question explanations that I don't understand, but I am perfectly willing to be proved wrong, as I will have learned something along the way.

No worries here. Sorry if I came across that way. Just putting in my two cents.

Now, as you most likely know, we are going to say "no sink traps are to be below the floor". Another code thing here in the states. However, I need to re-adjust my thinking for this one. Fact is, you will most likely be doing a better job than most houses in that area if you have any vent at all, yes? Believe it or not, years ago, many homes even in the states were plumbed much like your first pic. Things just gradually changed as they found the problems with such installs, but many of them homes are still around with no problems to speak of. I would still suggest keeping the sink trap above the floor (in the vanity cabinet) for easy access in the future. AAV (see pic) would work nicely here for you. I have no doubt that you are a well educated and experienced, but as you know, modern plumbing is a different monster than it used to be. Glad you are trying to at least make things better in your new home than what the standard there is. Good luck on your project, and take care. Lee.

On a side note: Years ago, my father-in-Law plumbed his new bathroom himself bcs he "knew how to do stuff." He was a builder, after all and too proud to ask me to do it for him. Well, when you come to his master bath today, first thing you notice is a mild sewer odor caused by absence of P-Trap in his floor drain. Then, when you flush toilet, you hear water rushing all the way down to the City Sewer. The sound comes from the floor drain and shower. Again, no P-traps. Does his system work. Sure it does ! Is it plumbed the way it should be ? Absolutely not. My Mother-in-Law complains about the smell but I have never told her. I just plug my noise when visiting.

Quote:

Originally Posted by mygirlsdad77

No worries here. Sorry if I came across that way. Just putting in my two cents.

Now, as you most likely know, we are going to say "no sink traps are to be below the floor". Another code thing here in the states. However, I need to re-adjust my thinking for this one. Fact is, you will most likely be doing a better job than most houses in that area if you have any vent at all, yes? Believe it or not, years ago, many homes even in the states were plumbed much like your first pic. Things just gradually changed as they found the problems with such installs, but many of them homes are still around with no problems to speak of. I would still suggest keeping the sink trap above the floor (in the vanity cabinet) for easy access in the future. AAV (see pic) would work nicely here for you. I have no doubt that you are a well educated and experienced, but as you know, modern plumbing is a different monster than it used to be. Glad you are trying to at least make things better in your new home than what the standard there is. Good luck on your project, and take care. Lee.

Thanks for understanding, and thanks for the useful information. (That goes to everyone who answered my original post... MOST appreciated).

As it turns out, I am going with <massplumber>'s recommendation, as my builder said he could install the PTRAPS for the sinks above the floor as I originally had hoped.

I had previously changed the original design to accommodate what I perceived as a routing difficulty due to the nature of the all-concrete construction that's done here in Thailand as standard practice (one of the positive aspects of Thai construction practice). However, my builder subsequently showed me how to accomplish the original design, so PTRAPS above the floor it is.

I am today demonstrating the proper installation of CEE (Ufer) ground to my builder. I will also be meeting with both the architect and the builder to discuss their reasoning for using "wet" concrete. What makes everything such a challenge is that I speak almost no Thai, the builder speaks no English, and the architect speaks very little.

Anyway, thanks for the assistance. It really is much appreciated.

Good luck with your project ! Keep us updated, perhaps with few photos ! Would be interesting to see how they build there ! Best ! Milo

If you are interested, you can follow the house build at the following link. Just look under the Thailand photo album:

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