How to Repair a Kitchen Sink Drain Trap | This Old House

How to Repair a Kitchen Sink Drain Trap | This Old House

all right now underneath any kitchen sink or any sink there should be a trap and normally the trap water goes here and it goes right out through the wall so there's a water seal right here and that water seal is really important to keep sewer gas from come up inside the building look at this whoever rough this kitchen sink and put the drain way up here so that means that this entire pipe is now filled with water so this entire pipe is the trap and that's why we see water right at the base of this ball on the left-hand side now the other thing I notice is something I don't think I've ever seen in all my years in plumbing when I did the house listing it was it listed as four bedrooms and three traps you have three traps underneath the kitchen sink this one for this bowl one trap for the right-hand Bowl and one for the dishwasher now what I want to do is to actually fix this the right way which means I'm going to get rid of all this piping and bring it all together into one trip all right okay all right good okay this one so we're going to do is simplify this pipe right now there are three holes going out through the back of the cabinet and we only need one so this one on the upper left we're actually going to cap the one here on the lower right we're going to plug but use a clean-out and that will allow us in the future to clean this drain should we need to these connections will be cleaned and then glued with PVC connections I want to be sure I get cleaner and glue on both the inside of the fitting in the outside of the pipe all right now before I start we're on the tubular piping I like to reinstall the disposer next couple of reasons for that if I install the disposer it helps me establish exactly where this drain pipe comes down that helps me determine the length of this pipe to be cut it also lets me address the dishwasher connection that you had a separate trap for your dishwasher and here's the connection right here from the discharge pump well any disposer actually has a tap in right here made just for the connection to the dishwasher you can see it right here and behind it is a knock out if I take a screwdriver I can knock that thing right out alright just find that not good good alright now we can reinstall the disposer good all right so I've tightened up this connection to the disposer L right here here's our trap that's in place and now I need to install this T fitting that will give us the branch going over to the other sink but you notice that this is actually too long it wouldn't fit in the trap so I need to mark it right about here and cut it guide it in until you get that in the window look at that huh perfect huh alright so we have our T fitting in place I'm going to just snug up the nuts both below it and above it all right now I have two more measurements to make and two more cuts one is this waste arm that's going to come over here and go to this point they're going to hold it in place and you can see that it can only go this far so I want to mark it okay but I also need to mark this vertical piece I want a little bit of pitch here so that's about right right about there and I'll cut them all right this is your – all right so our last connections to make it for this waste time the horizontal piece good my last connection is the discharge hose from the dishwasher and I'm going to make the connection to this bar using the stainless steel clamp all right Cheryl I have checked for leaks there are none but I want you to give it a try okay look at that the water is going down down down and out of sight thank you so much Richard I really appreciate you coming down to Georgia to help me out you

6 thoughts on “How to Repair a Kitchen Sink Drain Trap | This Old House

  1. Is it necessary, or even desirable, to connect the DW drain to the disposal? Does the disposal slow down the drainage? Don't these plastic fittings come with small outlets to attach the DW drain, of course before, not after, the trap.

  2. the dishwasher discharge does not meet code, you are required to have either an air gap or a stand pipe with trap. going to the disposal with out an air gap is a total hack job. I just lost all respect for Richard.

  3. Using the upper pipe is a really bad idea because now the entire horizontal pipe is at trap height and will stay full of water, this means both that draining water has to push a long plug of water, and that once draining stops there is a long stretch of pipe for particles to settle and form clogs.  Having a clean out is silly anyway since traps should always be removable and thus you already have a clean out. FAIL Richard.

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