I am installing a dishwasher in a peninsula opposite the sink. A drain line of 8' will be required. I have good access for all services from below. The drain hose on the new dishwasher loops over the top of the dishwasher, so that gives me my rise. From there I will go under the floor to the sink area. I am unclear from here. Do I go up and into the sink drain above the trap, or can I stay under the floor and go into the 1 1/2" horizontal drain line, before it hits the 4" main drain? Some guidance would be appreciated. Thanks

If you do not connect back to the sink you will need an air gap fitting on the countertop to prevent siphonage.

use a dishwasher tee at the fixture discharge just like a regular sink

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"Measure Twice & Cut Once" - Retired U.A. Local 1 & 638



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Thanks for the reply. Please clarify, siphonage from where to where?



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Thanks for the quick reply. A little more explanation is needed. I'm not sure how this answers my question.

siphonage from the sanitary pipe into the dw

iow - @#$%& into the dish holder

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"Measure Twice & Cut Once" - Retired U.A. Local 1 & 638

My drain line will loop over the top of the dishwasher. Does that affect the siphonage? Also does connecting above the sink trap, or into the drain pipe under the floor make a difference? Thanks

Quote

Also does connecting above the sink trap, or into the drain pipe under the floor make a difference? Thanks

YES YES YES a BIG DIFFERENCE

connecting above the sink trap provides an 'air gap' of sorts (when the sink is empty)

you may NOT connect the dw hose w/o an independent and vented trap - the hose itself does NOT form a code compliant plumbing trap, merely serves to keep the pump 'wet' and act as a 'high loop' (where code permitted



you may replace the red piping in the island sink sketch with an Air Admittance Valve (AAV) - local codes permitting - not best practice, but minimally acceptable

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"Measure Twice & Cut Once" - Retired U.A. Local 1 & 638

My kitchen sink is vented horizontally for about 2' then vertical out the room. This vent comes off the vertical drain pipe. about 1' below the sink trap. Is that adequate venting?

NO NO NO

the ONLY way to vent an island sink is either:

above diagram

or

AAV

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"Measure Twice & Cut Once" - Retired U.A. Local 1 & 638

i think my friend from SC it telling you to treat the dishwasher like a washing machine. add a trap in the cabinet beside the dishwasher and vent it with an AAV or island vent. the drain hose from the dishwasher would stick into a standpipe.
if you want to run a long drain hose under the floor and up into the trap across the way, you should check with the manufacturer to see if the pump is strong enough.

A 8' run, I would run the drain hose back up into the cabinet base and into a dishwasher tailpiece in the sinks drainage system.

ditto

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"Measure Twice & Cut Once" - Retired U.A. Local 1 & 638

Thanks all for the input and advice on this issue. My plan is as follows:

1. Route my discharge hose directly down under the floor. Eliminating the loop over the dishwasher will allow me to shorten the length of the hose.
2. Run the hose 6.5' across the kitchen and turn up into the sink base cabinet.
3. Run the hose vertically, form a high loop, and back down into the sink drain, above the trap.

Basically all I have done is add a 6.5' horizontal run to a basic installation. I don't believe this extra horizontal will adversely affect my pump. I haven't decided yet on what type of hose to use, but may go with a smooth walled one to help ease the strain on the pump (?).

Anyway, Thanks again for the help.



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make SURE you have the FACTORY REQUIRED (and generally 'built in on the back') 16" loop above the pump assembly


it is your nickel to run d/w tube in a concealed space

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"Measure Twice & Cut Once" - Retired U.A. Local 1 & 638

My high loop will be under the sink.
I have a basement, so all of the underfloor drain hose is easily accessed from below.

Thanks