Hi Everyone.
I am plumbing my house from scratch. The stack pipe is at one end of the house and I have run a wast pipe horizontaly along the floor upstairs 16 meters, it has a fall of 25mm per meter. There is a toilet connected with a swept t at each end and one in the middle.
I meter uphill from the middle toilet connection to the main pipe I have a T with a cap for rodding. I got my wife to flush loo paper down the middle toilet whilst I looked in the rodding point. The water started going the right way and about 2 seconds into the flush I noticed water and paper flowing the wrong way past the rodding point then after a few seconds it turned and all went the right way. the paper got hung up on the connection of the rodding point.
I can see what is happening, as the huge torrent of water from the toilet goes into the swept T it's swept down the pipe, as the pipe is so long and the fall slow the water is flowing away slower than the water entering the pipe, at the point of the T the resistance of the water flowing downhill is greater than the 0 resistance of the air behind it so the water flows backwards uphill untill, there is a point where the forward flowing water is at the same level as the backward flow then the direction changes so it all goes downhill. Phew.
My question is On such a long run with a slow fall should I have used Y connectors with a 45 on the Y so as to make the wast pick up speed and be slung more directly in the direction of flow rather than with the swept T which is more like a very steep bend with a flat wall in front.
Any advice much appreciated.
regards Mark.
I am plumbing my house from scratch. The stack pipe is at one end of the house and I have run a wast pipe horizontaly along the floor upstairs 16 meters, it has a fall of 25mm per meter. There is a toilet connected with a swept t at each end and one in the middle.
I meter uphill from the middle toilet connection to the main pipe I have a T with a cap for rodding. I got my wife to flush loo paper down the middle toilet whilst I looked in the rodding point. The water started going the right way and about 2 seconds into the flush I noticed water and paper flowing the wrong way past the rodding point then after a few seconds it turned and all went the right way. the paper got hung up on the connection of the rodding point.
I can see what is happening, as the huge torrent of water from the toilet goes into the swept T it's swept down the pipe, as the pipe is so long and the fall slow the water is flowing away slower than the water entering the pipe, at the point of the T the resistance of the water flowing downhill is greater than the 0 resistance of the air behind it so the water flows backwards uphill untill, there is a point where the forward flowing water is at the same level as the backward flow then the direction changes so it all goes downhill. Phew.
My question is On such a long run with a slow fall should I have used Y connectors with a 45 on the Y so as to make the wast pick up speed and be slung more directly in the direction of flow rather than with the swept T which is more like a very steep bend with a flat wall in front.
Any advice much appreciated.
regards Mark.
Can you upload a photo or diagram of how the middle swept T is connected. Also 25mm/metre seems a little excessive. Waste pipes need to be only slightly above horizontal although I forget the exact mm/metre that is required. 
