Plumbing an unusual dishwasher setup
rfarnham
| Posted in Construction Techniques on
For floor plan reasons it’s not worth explaining, I need to separate my kitchen sink and my dishwasher. They will be far enough away that I need to figure out how to plumb the drain for the dishwasher without it going through the sink tailpiece or disposal.
I haven’t bought the dishwasher yet (I’m in the rough-in phase) so I don’t have any instructions to work with. I know that dishwashers are often routed to an air gap in the counter top, or at least just below the counter. Would I need to do this if it had its own drain? Would it be a standpipe like the washing machine, or is there a way to rig a more conventional trap?
Any suggestions would be much appreciated!
-Rich
Replies
I will start by saying I am not a plumber, but have done some of it. The main thing to consider is that the air gap for a dishwasher breaks the vacuum so you cant flood the dishwasher full of dirty back up water. It is also normally next to the sink so as to allow any splash back in the gap to end up in the sink, and not all over your counters. Sorry I am not more help, but I bet good advice will be here shortly.
Dan
I see no reason you can't use a separate drain for the dishwasher. Just be sure to put a trap in the line and tie into your vents. You might also want to make provisions for accessing the trap/drain in case it every gets stopped up.
I once went through the floor with a dishwasher drain line and hooked it into a 2" line that was in the basement. No trap, no vent and it never stopped up so I am not even sure a trap is needed. The sump in the dishwasher always has some water standing in it, so it acts as a trap.
I have also hooked them up at some distance from the sink and ran the drain/water lines through as many as three cabinets to reach the sink dw tail piece. No problem with any of them that I ever got called back on.
None of those installs were ever inspected because they were just relocations of existing equipment during remodels and inspections weren't required. On new construction, you might want to float your proposal by the plumbing inspector before you waste time and material on something he may not approve.
Dave
Your local code may or may not require an air gap. Check code before you install the unit.
It cost me a service call learn that, yes, you will need an air gap. The warrantee did not cover mistakes made in DIY installation. (and of course the instructions - instructions? - said to put one in)
Old machine worked fine without the air gap, but without one the new machine siphoned off a lot of the wash water and dishes didn't get clean.
You will also need a trap somewhere in the waste line.
Might be cheap insurance to check all the particulars with your plumber or service person.
Good luck,
oldfred
It cost me a service call learn that, yes, you will need an air gap. The warrantee did not cover mistakes made in DIY installation. (and of course the instructions - instructions? - said to put one in)
I had to laugh reading this. I did a kitchen for a friend. The plumber hooked up the dishwasher, but I got it in place and attached it to the cabinetry. The first load of wash was fine, but the second leaked a little. I looked at it, and it was a different design than I'm familiar with, but I couldn't see anything wrong. On the third load, the entire kitchen flooded, which wasn't very good at all.
Since I had no idea, they called the Maytag guy. Turned out the plumber had left in the shipping plug (bright orange) in the drain hose. What amazed me most was the charge for the service call: ZERO! That's customer service! (Don't think it had anything to do with DIY vs Pro install, though.)
I can't kick - I've been given several good breaks from service reps. Just not that time.
I'm trying to figure out why your first load didn't leak. Or do you mean the first rinse of the first load?
I'm trying to figure out why your first load didn't leak. Or do you mean the first rinse of the first load?
Nope, the entire wash cycle ran without leaking. The 2nd entire wash cycle only leaked a little (mop up with a towel type leak). I probably should have noticed more water in the bottom than there should be, but I didn't know what was normal. On the third load, it was finally really obvious something was dramatically wrong. This sounds unlikely, but if you think about it, first, a dishwasher doesn't use all that much water. Second, it has a float switch to make sure the water doesn't get too deep, so that might have prevented more flooding.
I just did this in a house a few months ago. I put in a vented line with a ptrap in 1 1/2" abs. Above the trap I put in an abs tee that has about a 11/2 " long ridged tee that accepts the discharge hose from the dishwasher. Above the tee I glued in a permanent cap. In the wall behind the dishwasher I left a small access.
Have a good day
Cliffy
That is the kind of solution I was looking for. I couldn't figure out how to connect the 5/8 hose to the PVC of the drain system. I don't know why I didn't think of just using a dummy sink tailpiece and covering the top. I am still considering the suggestion of some to just lengthen the drain hose to reach the sink, but don't like it that much. There will be a fair amount of friction in a hose like that and making it too long seems like it will present problems. That being said, I don't really want an air gap sticking out of a random area of my counter either. Running the longer hose would get the air gap back to the sink which would be good if it did clog.Guess I'll just keep thinking about it...Any other thoughts out there???-Rich
The purpose of an air gap is to prevent siphoning water from the sink back into the DW. If you drain directly into a trap somewhere else, there would be no need for an air gap. If you drain into a standpipe with trap, like for a washing machine, that in itself is a kind of air gap. It could be installed at the back of a cupboard with a washing machine-like J-pipe terminating the DW drain hose. BruceT
No
Yes an airgap prevents back siphonoge , but if you tie directly to a trap then you lose the antisiphon feature.
What water is worse--- sink water or water in the actual waste pipe.When asked why is there four engines on a 747------ "cause we couldn't fit six" a Boeing engineer
You're assuming that the waste line downstream becomes plugged and there's no vent and there is nothing lower than the top of the DW drain hose (you always loop the drain hose as high as possible) to let the back up escape? OK, THEN it could siphon.Living in a one story house, I forget that there can be drain water from upstairs to contend with.Standpipe solves those possibilities.Another possibility is to run DW drain hose high under counter, install a "Y" at top of arc with one end running across to an air gap on the sink deck; other leg of "Y" going straight down to a trap close to the DW. Short run for drain water, no siphoning, and DW water goes into sink if its drain line is clogged somehow.BruceT
If you leave a 1" air gap between the discharge hose & any drain, then you meet code & eliminate any possibilty of back siphon.When asked why is there four engines on a 747------ "cause we couldn't fit six" a Boeing engineer
Gotcha.ThanksBruceT
Have you ever seen or heard of an actual back siphon from a dishwasher?
I haven't in 30+ years of remodeling and construction, but I'm not a plumber so I don't see all the bad shid that happens.
Just curious.
Dave
Yup.
Seen a few that just had the discharge hose "looped under the counter" that would draw back waste water from the disposer everytime the pump would shut off.
That's a double failure to have that happen though.
First the pump letting water back through it, second the disposer plugged up enough to have a standing water situation in the disposer.
Not that common to have that happen though.When asked why is there four engines on a 747------ "cause we couldn't fit six" a Boeing engineer
Thanks.
I didn't use a sink trailpiece. It was an actual abs fitting, so everything is a glued connection except for the dishwasher drain hose to the abs piece, which is double hose clamp. This is all in the wall behind the dishwasher (interior wall) so there was no need to extend the dishwasher drain hose. In one of my houses I ran an extended drain hose under neath the cabinet behind the toe kick. I'm more comfortable with a glued abs connection. Not much PVC around these parts in residential.
Have a good day
Cliffy
I am still considering the suggestion of some to just lengthen the drain hose to reach the sink, but don't like it that much. There will be a fair amount of friction in a hose like that and making it too long seems like it will present problems. That being said, I don't really want an air gap sticking out of a random area of my counter either. Running the longer hose would get the air gap back to the sink which would be good if it did clog.
You might want to check with the dishwasher manufacturer. I'm pretty sure the last dishwasher I installed came with pretty detailed instructions about this stuff (distance from sink, size of tubing, etc.). As others mentioned, check your local codes to see if an air gap is required. They can be a pain (leaks), plus they use up a hole in the sink.
Not sure about the vacuum break, but the need for it seems reasonable.
For further information, most recent-vintage DW's I've seen require that the flex drain line rise to nearly the top of the unit before going elsewhere. I belive this is done to ensure that when the DW drain pump stops that enough water drains from the line back into the DW sump to ensure a vapor-barrier exists.
Brooks
Couple of things.
You could do a "johnson tee" or an indirect drain.
I know I have posted pics or drawings of "johnson tee" in the past if you do a search look johnson tee posted by me somethin ought to pop up.
Indirect drain would be a trap with a reducer on top acting as a funnel, & the dw disharge hose terminating atleast 1" above the trap opening.
Ofcouse that would have to be accessable, so it might take up room in the cab next to the dw
When asked why is there four engines on a 747------ "cause we couldn't fit six" a Boeing engineer