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4just1don 01-06-2009 11:46 AM

Dynamics of 3" vs 4 " main sewer line
I cant remember who told me this MANY years ago,,,but they said a 3" sewer pipe works much better than a 4" sewer pipe. Reason was the curve of the pipe carries more water so solids float better down the pipe. Also said anything that a 4" pipe will handle a 3" will also!!

Was who ever told me that full of crap??

I am thinking of changing out a 'cast' stack and wondered IF a 3" PVC pipe meets codes??? All would be connected to 4" cast at ground level in crawl space. MOST is vent stack straight up. Very small 600 foot house,,,stool is about 4' from vent stack,,tub about 6', bath sink less than a foot,kitch sink 2', washer drain 1'.

Cast stack is all rusty below a certain joint,shiny black above,,might be leaking,(it is cocked at a weird angle) plus some yahoo didnt block off a old washer drain and IT backs up and dumps in crawl space as evidence proves. Dunno how the gas smell didnt get bad,it is trapped, but that has to dry out to. Bathtub is worst,,,galvanized and cast,,,probably gunked 90 % shut,,,hard to tell. Cleanout rusted badly. NO chance of ever adding house footage or second story!!!

Just thought I could clean up this potential problem pretty cheap and easy. one story house with walls removed now anyway,3' or less in attic to go also!! So looking at UNDER 20 feet all total of 3 or 4 " and 10 feet of 2"

DUDE! 01-06-2009 04:18 PM

someone pointed out on here that with all the water saving devices available, toilets, showers, etc, that the four inch is too big diameter, or at the very least, it will lead to more blockage because of less volume water in the pipe.

4just1don 01-07-2009 12:40 AM

Thanks DUDE,

thats what I heard also. In rethinking this 4' to the stool is only horizontal pipe of 3 or 4 " ,,,all other is straight up and down where 3" doesnt look to be a problem at all!! I am SURE the top portion sticking out the end ,of the roof is 3",,,seems 3" can suck all the air it needs,,,right?? I always thought it helps keep birds and squirrels out of climbing down inside too,,,those old 6" cast staks out roof was a nesting spot for every bird in the county

Whats disturbing is I saw the rubber boot over the pipe deteroriated faster than the shingles did and is leaking badly,,,Is there a better brand of rubber boot for roofs??And cheapo brands?? (its on a temporary duct tape seal till roofing weather). going to change vents of that attic while reroofing!!Will boots last longer then?? Whole house,,600 square feet,, has small gable vent only,,in each end!! Going to switch to continous soffit vent with ridge vent on roof

DUDE! 01-07-2009 06:37 PM

Maybe be better to ask the roofers about the boot. I've seen them covered differently when shingleing. I figure if the shingle is over it, it would be better but I have no proof on that. My son's house, came with not too old a roof, must of leaked around the vent because there is alot of goop all over its base. I didn't care for the ones I seen at hd last I looked, although I got one there a few years ago when I did my roof over that seemed stronger that what is there now.

4just1don 01-07-2009 07:01 PM

I meant the rubber part of the boot

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