We are in the process of designing a waste pipeline and are seeking guidance on the best practice for connecting two WC units that are positioned back to back. Could you provide insight or recommendations for this scenario?
They are trying to add some slope as soon as possible.I dont know why or where a street 45 figures in to this and why any fitting would be required between the wye and the closet bend other than to reach desired location
got it for the inspectorThey are trying to add some slope as soon as possible.
good catch it will need venting, but thought he was asking if the drainage works Id say only under certain conditions would the left side drainage be compliant 1/4 inch per ft on the main and double wye wont cut it.Without adequate venting it is not a working system.
If the barrel is pitched, and you achieve the best case that the two branch inlets of the double wye are at exactly the same elevation, then those branch inlets are never completely "flat". Their pitch will be 1/sqrt(2) = 70.7% of the pitch of the barrel. So if you want their pitch to be at least 1/4" per foot, you need to pitch the barrel at least sqrt(2)/4 = 0.3535" per foot.I think Wayne calculated out how much fall the wye would need in order to provide fall for the 2 "flat branches" to have a minimum of 1/4 inch per foot.
thanks wayne I guess i remember correctly laying the wye flat with minmum fall clearly would not comply with enough fall for the branches . im getting a little technical because Ive had inspectors pick apart the smallest of things unless youve got gobs of fall exceeding the (absolute mathamatical minimum) by giving it over 3/8 " to 1/2 inch per foot on the barrel Id see it as a possible/ likely fail .If the barrel is pitched, and you achieve the best case that the two branch inlets of the double wye are at exactly the same elevation, then those branch inlets are never completely "flat". Their pitch will be 1/sqrt(2) = 70.7% of the pitch of the barrel. So if you want their pitch to be at least 1/4" per foot, you need to pitch the barrel at least sqrt(2)/4 = 0.3535" per foot.
Of course, getting the two branch inlets at exactly the same elevation is tricky; if you're half a degree off on the barrel rotation, one inlet is more pitched, the other inlet less pitched. So it's still delicate, and pitching the barrel a little more would provide a margin of error.
I think the point about putting street elbows in the branch inlets is that you can now rotate that joint to ensure that coming into the elbow you have at least 1/4" per foot slope. So if you were slightly off on the double wye's pitch or rotation, the error would be just for the length of the branch inlet portion of the double wye fitting.
Cheers, Wayne
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