I am installing a standard kitchen sink drain basket (3.5" on one side and a disposer on the other.

First question - how do I tighten this big nut? My largest plier can't go around it, should I use a plumber's wrench or should I use a mallet and flat head screwdriver to "tap and drift" until tight? How would I know if it's tight enough?





In the installation instructions it says to use the included rubber washer under the flange and no putty is needed. Is it better to follow instructions or is it better to throw out the washer and do it the traditional way with plumbers putty under the flange or the newer way silicone?





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Get one of these wrenches

There are many different types. The issue with tapping the nut tight is that it knocks the strainer off centre.

As to whether to use the gasket on top, it depends on how well the surfaces mate up. If the slope angles are very different, you end up with a very narrow area of contact and the gasket, along with a light coating of silicone, should be used. If the angles match up, there is a wide area of contact and just silicone will suffice. The gasket creates a small ring around the edge of the flange inside the sink where dirt accumulates and I prefer to avoid using the gasket whenever possible.

The jaw of a Channellock pliers works just as good a one of those wrenches.

100 % silicone caulk under the flange. the rubber goes under the sink and as hj said, channel lock pliers grab two of those tips very well.

george there is quite a bit of contact area between the flange and the edge of the drain hole. Since both you and Packy recommended silicone I will ditch the washer and use silicone instead. Good point about the washer raising the height of the flange just a tad to accumulate a bit of water. Thanks!

Next question is how best to connect the drains for the two bowls.

I am planning to install an Insinkerator garbage disposal on the left bowl, and a regular drain basket on the right bowl. In the past my preferred method is from the disposer I run a horizontal pipe straight out (without using the included 90 outlet elbow) and ties that into the tailpiece of the right bowl, than the right side drains to a tubular P-trap and the p-trap runs to the wall connection fitted with a trap adapter.

However, after doing some measurements I don't think this will work because the distance of the right tail piece is too far. I think the most a 1-1/2" p-trap can make up horizontally is 3" or so right?



What are my options?

(1) Cement onto the drain with a 45 PVC elbow and install a trap adapter to that, or

(2) Use an tailpiece elbow to go horizontal from the right bowl, and do the same on the left coming from the disposer and they meet in the middle with a baffle tee than a tubular p-trap into the trap adapter at the drain.

Is there a better way?

Don't throw away the gasket, use it under the sink as packy recommended. The gasket cushions the joint and makes it more resistant to stresses.

george thanks for pointing that out, yes I will put the gasket on the underside above the big nut. Now the manufacturer came with a really piece of same size circle to go between the bottom of the sink and the nut and I think it's like really thin cardboard. I guess I will put that under the gasket, and under that tightens the nut.

I think I will connect the drains this way.



From the disposer runs straight across and connect to the tailpiece from the right drain. Then down to a P-trap. From there to the wall the 6" distance is too much for the P-trap so I will cement at the wall a trap adapter, into which I will need a tubular 45 elbow (shown in red above). I will get a double offset fitting and cut half of it off to use the spigot end into the trap adapter, the other slip joined I will align with the outlet pipe coming out of the P-trap. I hope that will work.



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sum.. number one... slip joints on the outlet side of the trap are illegal in MA.

number two.. i don't like so many slip joints spread all around the cabinet. too many places for someone to push a roll of paper towels in and cause a leak.

Packy, no slip joint on the outlet side of the trap in MA, so you can't have a trap adapter at the wall? So in MA the only place to put a trap adapter is on the inlet side of a trap facing up? I thought one advantage having a trap adapter at the wall is to allow removal of the tubular p-trap to snake the trap arm and beyond if necessary?

MA requires a cleanout under a kitchen sink.

MA is tough. I do have an unused access to the drain to the right.

To me I prefer the trap adapter at the wall yes it means two slip joints after p-trap outlet but can't help it I need flexibility and serviceability.

sum... this is as far as MA allows us to do.

Wow, so no "toy grade" tubular piping at all except the sink drain tail piece!

no but its the version of p trap that we sometimes use to make drain cleaning possible thru thru undersink piping.

Packy, are you allowed to have a shielded coupling on the trap arm?

OK so I finished the undersink install of disposer (minus dishwasher still to be purchased) to the left bowl, the drain basket to the right bowl, and the tubular plastic components all the way to the 1.5" trap adapter at the wall.







I was going to use silicone under the drain flange but the half tube of silicone caulk dried up so I went back to old fashion putty. the gasket went on the underside as Packy suggested worked out great.

Yes, quite a few slip joints not ideal but hopefully will work. Filled up both bowls to the rim to test full draining as well as the undermounting of the sink to the new countertop.

This is the first time I used a double offset fitting cut in half to connect the p-trap outlet elbow to the trap adapter. In the past I would solvent weld a SCH40 45 elbow then put a trap adapter at the end of that, definitely more sturdy that way but I want to kept the option open to use that wall connection for the left bowl and some day use the right side drain (currently capped and abandoned) for the right bowl and having a 45 turning right makes this impossible.

I wish there is a way to make this joint stronger (the one in red).

Nice clean job Sum. Thanks for sharing all your experiences.

yes..
i've done a few modular homes that the sinks were all finished. they came thru with trap adapters on the trap arms.

had to cut out the adapters and use sheilded couplings

so Packy is the adapter is cemented into the 90 elbow behind the wall you had to open the wall too?

Thanks Vic, spoke too soon, initially no leak but once I filled the bowl 90% and pulled the stopper to test draining in full water was overflowing out of the disposer's dishwasher connection. I knocked the hole open during the install because there will be a dishwasher but I don't have it yet so I put on a dishwasher connector and used electrical tape on the end...which didn't work at all.

I then took an old dishwasher hose that I was going to throw away and cut the end off it, filled it with caulk and let set. This worked and will have to do for now until I order the new DW.

Packy here is one I did at a rental because the piping is inside the cabinet and I didn't want the tenant to overstuff the cabinet and mess up tubular pipes so I carried the SCH40 all the way to the sink cabinet and the P-trap with the trap adapter pointing up at the disposer down elbow.

they would love that in MA,,