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Running new kitchen drain because 1953 wasn't friendly with connection height

Running new kitchen drain because 1953 wasn't friendly with connection height

Old 01-31-17, 04:37 AM
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Running new kitchen drain because 1953 wasn't friendly with connection height

So my fiance and I are looking at replacing our sink in a 1953 house with mostly cast iron drainage. The kitchen and bath were remodeled in 2004 but the only drainage they replaced was a section from the shower to the main drain with a fernco insert into the cast iron drain. The problem we have ran into is the drainage connection for the kitchen is too tall to put modern depth sinks in and retain a garbage disposal. To access the old cast in the wall would be a complete chore because of it's location and would involve removing half the kitchen cabinets.

Therefore we need to lower the originating connection for the main kitchen drain. My thoughts were to either tie into the new pcv drain line for the shower to utilize the sewer vent stack for the bathroom and cutting off the old cast line to the kitchen and putting a rubber screw on cap on the end should the system ever back up. Seal off the vent stack with a cap also and then plug the drain hole to the kitchen with a threaded plug to keep anything from getting in via the roof vent. Then run this new line up through the floor in the blank cabinet space next to the sink.

Or another option thought was to cut the cast line just past the connection which is apparently somewhat built up inside the line since water isn't running in the pictures I took but while down there it was leaking out the bottom of the drain about 2 feet to the right of the connection and rolling down the pipe then dripping off right next to the pier under the house in the photos below. With cutting the old cast line I would also cut along the concrete footing at the opposite end to completely remove that section of pipe. Then use a slip on fernco pipe adapter/joiner to connect the remaining section of cast that is left after cutting just to the right of the fitting to pvc then like mentioned before running it up through the floor in the dead space of the unused corner cabinet area which is above the current old cast drain.

With going this route there wouldn't be a sewer vent for the kitchen area and I was looking at an AAV to use in place of the old case sewer vent/stack. If I use an AAV I know they have to be put on straight pipe after the p trap but can they be put to where they are higher then the bottom of the sinks? This way if the sewer line backs up there is a sign in the sink it is happening vs the water coming out of the AAV and all over the bottom of the cabinet or in the void cabinet area.

This is to lower the point of exit so we can use the deeper sinks available. With both of us wanting to go with a granite sink it limits our choices even more if we do nothing to lower the point of exit for the drain since we need 9" to the non disposal side and 7" to the disposal side as it sits now.

I'll put photo links below with comments above them to explain.

Current sink plumbing layout.

Drain line passage into the void cabinet space to the old cast upright which is too high and would be way more work to replace and lower.

Exit of the cast drain line and upright location that the kitchen drains into. I mentioned cutting this off right at the concrete and doing away with it other then what is in the wall and out the roof. Was looking at cutting through the floor above this pipe into the void cabinet space to run the new pvc drainline along with putting a rubber cap where I cut this and then a thread in plug where the pvc line in the void connects to the cast to block anything from crawling down the stack and into the house.

Kitchen drain connection which is leaking 2 feet or so to the right of the connection. Was looking at cutting it around the area of the 4x4 in the background. Just enough to attach a fernco to attach pcv to it.

This is where the rest of the old cast drain connects to the main line out to the sewer. It's the diagonal line in the back ground. The rest of this is the bathroom including the toilet, new pvc to the shower, and the vertical sewer drain/vent to the roof which has the tie in for the bathroom sink in the wall above.

Different angle of the bathroom connections/ drain setup. This was the first thing I mentioned above about tapping into the shower drain's pvc to utilize the bathrooms sewer vent for the kitchen also. I just don't know if the kitchen sink/disposal and the dishwasher would be too much added to this connection with the bathroom sink, toilet, and shower already in this junction. As you can see the above picture the kitchen drain connects further down the main line after the bathroom connection currently.

This is the sink my fiance is in love with.

There is also this one for $50ish more that already has the second hole drilled even though the one above has the ability to drill other holes.

If I go with the AAV device does it need to be placed under the sink or can it be placed in the void where I can utilize the current drain passage cutout to change it if need be? Also as asked previously can it be put in higher then the bottom of the lowest sink basin in case there is a backup at some point and time it hits the sink before flowing out the AAV so there is notice.

Also I picked up sweeping 90s to make the change under the house then from the void to turn toward the under sink area. I read later that for drainage dual 45s are better for drainage because they don't restrict the flow as much. Any input on this?

Also thoughts on disposal on the deeper or shallower basin and plumbing ideas from the sink drains to the break in the floor for the new drain? I've never redone plumbing before just replaced bad sections with the same stuff.
The drain line for the kitchen is 2" So I got a 2" fernco to join the old cast and 2" pvc to connect to it. Obviously the under sink drainage is 1 1/2" The AAV is either 1 1/2 or 2" Where is the best place to change the 2" into 1 1/2" and plumbing routing ideas?
Old 01-31-17, 10:26 AM
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If you can tap into a drain in the crawlspace, I would run a new drain to your sink and use an AAV in the cabinet. Cap your old drain and leave the vent as-is.

The AAV can go in the wall, but it needs to be accessible both for air as well as replacement as they do fail over time. Usually they are hidden behind an air register, but I'm not sure you'll have that much space in your kitchen (unless you have an adjoining wall or something.

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