Drains And Vents

[grin]

Any plumbers out there? I've looked at similar threads but couldn't find specific answers to my questions.

I'm buying a 2 story house in a Koolpunt Ville project in Chiang Mai and am dismayed at the drains I've seen in other houses already started. I don't see any evidence of any traps on the fixtures nor any air vents for the drains coming through the roofs either. I don't see any clean-outs and I also see a bunch of T joints and 90 degree elbows where I think Y joints and two 45 degree elbows would be less prone to clogging.

I'm familiar with two types of drain systems that I have seen in the US. Both types have traps and air vents. The older type I believe may be called wet venting and has all of the fixtures close to one soil stack which also doubles as the vent stack. The newer type has separate vent stacks from the soil stacks and each fixture has an vent pipe behind its trap going to a vent stack.

My knowledge of drains and vents is minimal but I understand some of the science behind it. The traps are there to provide a water seal to prevent septic gas from entering the house and to possibly deter vermin as well. With traps you should get smooth water flow and you won't hear gurgling noise from the drains. The air vents prevent the water seals from being siphoned from the traps. Vent pipes connect to the vent stack above the flood level of its fixture so that the vent does not become a drain. Also I think that the vent pipe needs to tap into the drain pipe before it slopes down below the water level in the trap.

In the construction that I have seen in the US all of the drain lines slope down to the soil stacks at 1/4 inch to the foot. My understanding is that if you have more slope then the liquids will leave the solids behind when draining. Also having a near horizontal drain may make it less likely that a plug will form and cause clogging or siphoning. Does anyone know if having initial vertical sections on the drains will make it more likely that plugs will form?

Is there any reason to believe that Koolpunt Ville is doing something that makes limited sense? Maybe they will have a trap for the whole house before each septic tank. But how is that trap vented? Does anyone know how they typically build their drains? Maybe the gray water doesn't go into the septic tanks. Then there would be no problem with septic gas on the gray water drains but then you would still have the vermin and gurgling problems.

How can I work with what is already used in the Koolpunt Ville project? The drains have vertical drops through the floor and then sloping drains that go to the stacks. On the ground floor there is limited crawl space but room for traps and there is a suspended ceiling on the first floor below the second floor drains. Actually I am assuming that the second floor drains run into a vertical stack and do not drain separately.

Installing traps with this construction seems to be easy enough but the air vents seem to be a problem. Toilets have self contained traps but do the vertical drops pose any problems with the trap? Where would I put the air vent on these lines? There seems to be enough room under the floors to put traps on all of the floor, shower, and tub drains. And there is no problem putting sink traps under the counters.

There are no vents planned through the roof but I assume I could put holes in the roof. Another alternative would be to put vent stacks on the back of the house that rise above the roof. Putting in individual vents for each fixture requires a bit of work. For sinks and toilets I assume the vent pipes could run up through the interior stucco like the water supply lines. For the floor, shower, and tub drains which would have traps under the floor it seems like the horizontal drain after the trap needs to be low enough so that a horizontal air vent connected to it after the trap still has enough room to rise 1/4 inch per foot to get to the vent stack. It seems like the vent pipes would still need to rise vertically near the vent stack to connect to it above the flood levels for their fixtures.

Doing some searching on the net it also seems like using AAVs is a possibility. I'm somewhat familiar with what we call a Studor Vent in the US. I believe it is just a brand name for an AAV. I've seen them in use on basement toilets that have been added on and once on a new kitchen island which had a sink.

It seems that large AAVs are made that could be put on a main stack if it was extended to the attic. It also seems that one AAV installed on the sink drain may be adequate for all of the gray water drains in each bathroom. Then maybe I could use one AAV for the laundry and kitchen which share a wall. I have no idea how the toilets could be vented with AAVs. Does anyone know if it is possible to do everything with AAVs? It seems like using AAVs would require fewer changes to the current plans. But do they work well or are there any known problems with using them? Do they even sell AAVs in Thailand?

Koolpunt Ville will refund the cost of any work I wish to get done myself. It might be easier to use a contractor that already knows how to install a western style drain and vent system. Is anyone aware of such a contractor in Chiang Mai? Or is anyone interested in designing it?

Sorry for the long post.

[Crossy]

I've moved this to the DIY forum where it's likely to stay visible for longer and get some sensible answers

In my experience, even simple traps are, omitted, either as a cost saving or out of ignorance

Insist on a simple system of P and U traps and a stack vent on the soil pipe to stop the toilet traps emptying and you should be good to go. Anything remotely complex will draw blank looks

[kamalabob2]

Crossy hit the mark. Do NOT under any circumstances look for any new holes in your roof!! We have septic tank vent pipes going up the side of our home and a garage. The blue PVC pipe is painted the same color as the building and it works. You can meet in person with very good technical advisors of many plumbing supply firms, pipe manufactures, a slick drain company or two all at the Architect Expo later this month in Bangkok at Impact Center. SLOPE on drainage pipes is possible in Thailand as is P or U traps under each sink. But as Crossy warned any real "complex" ideas or concepts will be met with a blank look. Do a PRESSURE test on your pipes BEFORE they install the tile over the pipes. Stop Valves on every inlet is advisable.

[DrDave]

I'm not a plumbing expert, but what I've seen in my own house and others has caused me to make some mental notes for any future house I build.

If you can get hold of the detailed plans for your house from the developer, there should be a section that details the wastewater plumbing. This will tell you if they're separating out the lines for gray water from the toilet drains. Of course, what's in the plans, and what actually gets built are commonly two different things.

I think, as a general rule, traps are not used in Thailand. We have a newer home in Phuket, and I know for a fact that there's not a single trap on any drain line. In our case, the drains from the sinks, showers, floor drains and roof go directly to the sewer line out in the street (coupled through a concrete box with an air gap). We have no air vents, unless the roof drains are somehow doubling as air vents for everything else on the same stack (we have a flat roof with several floor drains). The major problem with this setup is that under certain conditions, gas from the sewer makes its way up the drain lines for the showers and floor drains, and in some cases, the sinks (if their P-traps are dry), leaving a nasty smell in parts of the house. Opening the windows in the house only makes it worse. I actually saw this explained in a Thai house & garden magazine once - they had an illustration that showed how the air current moving through the house causes a suction on the shower, floor drain and sink drains, effectively sucking sewer gas into the house.

Again, I'm no expert but I think you're on the right track with getting air vents installed for the sinks and toilets, and traps for the showers and bathroom floor drains. Depending upon your style of roof, the builder may be reluctant to punch a hole in the roof for one or more air vents, in which case running the air vent lines up the inside of an exterior wall, and then out at the top seems like a good alternative.

[longball53098]

I agree with Crossy. Anything complex and different from the "NORM" will get resistance and smiles and then they will do it their way anyway as soon as you leave.

Maybe let them build it first and then if you are a DIY'er you can come back later and make some changes and mods to suit you're needs. It may not be the perfect solution but it may some some headaches.

[bojo]

Just a thought, I'm afraid you've baffled me with all the technical stuff, however I'm assuming that the developer has various sub-contractors doing different jobs on site and that it would be possible to talk with the plumber prior to installation, but don't be surprised if they are confused as they will have been making drains their way for years.That will be the cheapest option. I do however know a Thai contractor who lived in the US, his name is Adam and his phone number is 081 7165378. He speaks excellent American and is very accommodating and always explains everything very clearly. He should be able to find you the right sub contractor, if you explain exactly what you need.

Also to consider, as far as I know, Koolpunt have been building for years Chiang Mai. I have never heard anything that would put me off buying with them. Their prices seem to be higher than most Moo baans in the city and their quality is much higher. With all their years of experience, would the Thai way not be the best way to go... Let them build it their way, I'm sure it will work just fine and if in the future it breaks, get it repaired as the locals do. You could also convey your concerns to the developer and try to get them to write a clause in your house purchase contract covering specifically the drains.

Regards Bojo

[grin]

Thanks for all of the suggestions so far.

And, Crossy, thanks for moving this thread to the DIY forum. I think your advice is probably spot on.

I was able to get Koolpunt Ville to send me a PDF file of the drain system drawings. I will try to attach the file.

Koolpunt_Drain_System.pdf

The first page shows the first floor and the septic tanks and the second page shows the second floor. Several things are obvious from the drawings. First is that the gray water drains are separate from the black water and do not go to the septic tanks. Second is that there are three columns of stacks. An interesting observation is that the four most used toilets all drain to the septic tank in the back and the two least used toilets drain to the septic tank on the side. The septic tanks seem to be for pre-treating the black water before directing it to the public sewage system.

The drawings are not isometric and seem to be missing information. For instance they show 4 types of pipe S, W, CW and V but I only see the four inch S pipes as being marked on the drawings and they are obvious anyway. The interesting thing is that the V type of pipe is shown to be a one inch riser to the roof so maybe they do at least vent at least the black water stacks.

However, as I said before I have seen no holes in any roofs but maybe I did not look closely enough for exterior pipes. So if I am lucky maybe all I need to do is make sure the gray water stacks have vents and then make sure all of the gray water drains have traps. In the drawings it looks like most of the gray water drains just tee into the horizontal drains below them. Maybe the horizontal drains could be lowered a bit so that traps could be fit in above them. If there is not enough room to do that then the traps could be placed next to the horizontal drain. Then I think they still need to connect to the horizontal pipes with vertical tees and not horizontal tees.

Any comments on putting in the traps? Do they sell integral two inch PVC traps here? I.e. where the trap is not a bunch of elbows glued together? Any suggestions of the type of traps to use?

I do like the idea of not having holes in the roof. Maybe one vent pipe could be connected to both the black and gray water stacks in each of the three vent columns. The vent pipes could come out of the house under the eaves and then go horizontally for about a meter to clear the eaves before going vertical again. Any suggestions on how high the vent pipes should go above the edge of the roof?

Koolpunt Ville has been quite professional in the front office. I have an account rep who is also doubles as the interpreter. I have been fairly amazed at her knowledge of construction although I do have small problems at times when she uses what I assume is British construction terminology. Both the main architect and the assistant architect have been quite good at explaining in detail why certain things I have requested do not make sense and more importantly they do come up with alternatives that do make sense.

I have a meeting scheduled with the architects for 10 AM tomorrow (Wednesday). Anything I should be asking them?

[grin]

The meeting with Koolpunt Ville went well and pretty much as expected but left a few more things that I need to resolve.

It was confirmed that the three soil stacks for the toilets are indeed vented. They found a house in the right stage of construction so I could look at how this was done. The attached crude drawing of the master bedroom toilet drain shows what I saw. Before the toilet drain makes the vertical drop into the soil stack there is a 2 inch air vent attached to the top of the drain which goes up about a foot and then it looks like it goes horizontal with a 1 1/2 inch pipe through the exterior wall. The vent is cut off even with the exterior wall. Toilet_Drain_Vent.pdf

They also had no problem venting the gray water pipes the same way that they were doing the black water vents. They already have traps on all of the fixtures but are only using the little bell type traps on the shower and floor traps. They agreed to switch these out and put in P traps. The main thing is that they understand the concepts of traps and vents so now it is just a matter of adjusting things.

Here are the major problems I see with the vents as they are now. The air vent is really small and not 4 inches, it is horizontal and not vertical, and it is nowhere neat the height of the roof. If any sewage backs up it will just drain out the side of the house as the vent is lower than the toilet.

My first thought is to just run the four inch stack out the wall at this point and up the side of the house to just below the eaves and vent it there. All 3 of the stacks are very near bathroom windows but nowhere near bedroom windows. One potential problem however is that odor could possibly enter the attic through the air vents under the eaves. At least these stacks on the back of the house and on the side with no yard so if I extend the pipes up the walls and paint them the same color as the house it should be quite acceptable.

One nice thing is that they build the brick wall around the column after the pipe is put in place so things can easily be changed now. The main structure of the house is now in place and they are starting on the roof but no plumbing is done except for holes in the concrete flooring. I probably have about a week to finalize what I want them to do.

My main worry is venting possible odor from the septic tanks. I think that using the small air vents as planned would work fine to prevent siphoning of the toilets. Anyone have any feedback on whether I should enlarge the vents to 4 inches? Or whether I should take the vents up the walls higher externally?

[Naam]

i think you worry too much Grin. during the construction of my house 4 years ago i was busy preventing or rectifying the sh*t which happened on a daily basis and therefore had no time to bother with vents. only later i realised that except for the 2" vents of the septic tanks no other vents were installed. the vents of the septic tanks are just a few centimeters above ground level. i have checked them umpteenth times because one is near the window through which fresh air is drawn by a whole-house fan for an hour every day. 4 persons living in the house using 4 bathrooms, never realised the slightest smell and all toilets are flushing perfectly without vents. my experience makes me think that the whole "vent thingy" is nothing but overkill.

and now i'm waiting patiently for the plumbing experts to crucify me

[grin]

You may be right. I am worried about the smell quite a bit and like you find something being done incorrectly every time I visit the construction site. The building foreman seems to only work from the plans. However, as he is used to building all of the houses the same he misses some of the details that are changed in the plans. He does not speak English so I have to speak with the front office to correct things. They do not seem to actively manage him to make sure he is following the plans so that seems to be my job.

I certainly don't expect the house to be built up to any international plumbing code plus if it works it works. There is no reason for overkill. However, I have lived in 3 cities in Thailand for 7 years total in 4 different rentals of fairly new construction in semi-upscale areas and they have all had sewage odor problems inside. I may not be able to do anything about the smell outside if the whole neighborhood smells bad but I would sure like to relax inside my home without smelling sewage.

In the US before they had venting figured out they used to have whole house traps to keep sewer gas out of the houses and there were some pretty famous disasters where sewer mains exploded. Without anything to relieve the pressure the explosive gases just built up. Essentially the sewer mains are airtight and the vent stacks in all the houses are the vents for the mains. That is why the US requires a 4 inch vent stack all the way from the sewer to the roof of the house. The sewer mains have no venting at ground level and are only vented through all the houses above roof level. This is also a pressure equalization system in that it not only serves as a vent but can relieve negative pressure in the sewer mains. You can think of it as allowing the sewage system to breathe.

It may well be that the sewer lines in Thailand are not airtight. They certainly won't be if there are vents on the septic tanks between the sewer main and the house. In my limited experience with septic tanks the vents are only needed if you have a drain field and vents are not needed as in my case where the septic tanks serve only as pretreatment before the sewer mains. Maybe the vents are not needed here to equalize the pressure from the mains but only serve the purpose of preventing the water from being siphoned out of the traps. If the vents are not needed so much for the sewer mains and septic tanks then maybe the small size of the vent and the height above the ground does not matter that much. I'd especially like to see people's thoughts and ideas on this. Any comments?

Anyway, once all of the drains and vents are in place and covered up it would be a nightmare to repair them as concrete floors or suspended ceilings would have to be torn out. And of course the idea of paying a bunch of money for a house that smells bad just does not sit well with me.

[trogers]

i think you worry too much Grin. during the construction of my house 4 years ago i was busy preventing or rectifying the sh*t which happened on a daily basis and therefore had no time to bother with vents. only later i realised that except for the 2" vents of the septic tanks no other vents were installed. the vents of the septic tanks are just a few centimeters above ground level. i have checked them umpteenth times because one is near the window through which fresh air is drawn by a whole-house fan for an hour every day. 4 persons living in the house using 4 bathrooms, never realised the slightest smell and all toilets are flushing perfectly without vents. my experience makes me think that the whole "vent thingy" is nothing but overkill.

and now i'm waiting patiently for the plumbing experts to crucify me

Vents are installed in vertical stacks to prevent suction and compression of a falling column of water affecting the water held by P or S traps. You do not need any vent if you do not have a vertical stack, ie. yours is a single storey building.

Edited April 30, 2009 by trogers

[grin]

Thanks, trogers, that fits with what Koolpunt Ville has in their plans. They have vents on the 2nd floor toilet lines but not on the first floor. The implication of this and the small vents sizes is that they are not concerned with venting the septic tank or sewer line. Yesterday I gave the following requests for changes for the drains to Koolpunt Ville:

Put in P traps instead of bell traps on the floor and shower drains and use one piece traps everywhere.

Add vent pipes to the gray water stacks on the second floor at the vertical drop same as the toilet stacks.

Use Y couplings instead of T couplings for drains connecting to the horizontal lines below them to allow easier snaking.

Last but not least do not cover any of the drains until I have inspected them.