Thread: Quest to Stop Dishwasher Drain Gurgling.....

The trap on the drain stops gasses and smell escaping from the drain out of the fixture / appliance.

With your plan what stops the gasses and smell from escaping via the dishwasher ?

Originally Posted by droog

The trap on the drain stops gasses and smell escaping from the drain out of the fixture / appliance.

With your plan what stops the gasses and smell from escaping via the dishwasher ?

Nothing......but this is why we ask.
I didn't realise THAT was the reason for using the S Bends.

Can that be cured or am I wasting my time?

Your question was will this work or not, I will say not. As per response above the design of the trap is to keep the open sewer smell out of the house.
how noisy is your dishwasher?? I not wish to sound harsh, but since dishwashers have been made they have connected them this way, early days the plumber would cut a hole in the side of the trap. Nowadays this is a moulded barb fitting. How old is your dishwasher??
given the number of dishwashers connected worldwide in this exact way if noise was an issue then why is there not more people looking to find a solution? My dishwasher makes noise but not enough to bother me.

I honestly can't see the sewer gasses working their way through the diswasher plumbing and drain pump. The sump in my D/W always has water in it too, so I assume that works as a trap.

However, with your proposed solution, I wonder whether the escaping dishwasher waste water might syphon out some of the sink trap water? The solution I use is to plug the sinks when the dishwasher is running. It almost completely eliminates the gurgling sounds when the dishwasher pumps out the water. We have the integrated plugs with waste baskets.

I imagine if you plumbed it the suggested way it would actually siphon the water out of the s-bend when the dw ran. You would end up with both noise and smell.

My coffee machine waste is plumbed in after the sink S bend and there's no syphoning of water out of the S bend. OTOH the volume of waste water from the coffee machine is significantly less than from a dishwasher.

Originally Posted by BobL

My coffee machine waste is plumbed in after the sink S bend and there's no syphoning of water out of the S bend. OTOH the volume of waste water from the coffee machine is significantly less than from a dishwasher.

Don't mean to burst your bubble Bob, but if there isn't a trap incorporated in the waste drain of the coffee machine, then technically this is not legal.
The waste from coffee machines is usually via gravity, not pumped.

Good practice for dishwasher waste connection would normally entail the pump hose to be affixed hard to underside of sink, creating a loop. This is quite often stipulated in the installation instructions from some manufacturers.

,

Originally Posted by capt'ngrumpy

Don't mean to burst your bubble Bob, but if there isn't a trap incorporated in the waste drain of the coffee machine, then technically this is not legal.
The waste from coffee machines is usually via gravity, not pumped.

Good practice for dishwasher waste connection would normally entail the pump hose to be affixed hard to underside of sink, creating a loop. This is quite often stipulated in the installation instructions from some manufacturers.

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Re coffee machine.
Correct, the waste should not be connected directly to any plumbing and should in fact be stopped above a trap and draining into a tundish, in turn creating an air gap as required by law and in turn stopping cross connection.

Re dishwasher.
Again correct.
Connection can be made direct to a sink trap, or to a separate trap, but same as coffee machine, with an air gap to stop siphonage.
The bowl above a sink trap acts as an air gap
For the purpose of fixing the hose high up the machine is usually supplied with a plastic U fitting approx 100mm+ in dia, which, when inverted, becomes the holding fitting for the loop.
Having installed a lot of dishwashers I have never seen a machine not supplied with the U fitting.
I have however been called to find out why water was still being left in the dishwasher and it was usually because the hose was too low and allowing water to drain back into the machine, often when the sink was flushed and even worse when a garbage disposal unit was installed in the opposite bowl.

Originally Posted by rambunctious

Re coffee machine.
Correct, the waste should not be connected directly to any plumbing and should in fact be stopped above a trap and draining into a tundish, in turn creating an air gap as required by law and in turn stopping cross connection.

Re dishwasher.
Again correct.
Connection can be made direct to a sink trap, or to a separate trap, but same as coffee machine, with an air gap to stop siphonage.
The bowl above a sink trap acts as an air gap
For the purpose of fixing the hose high up the machine is usually supplied with a plastic U fitting approx 100mm+ in dia, which, when inverted, becomes the holding fitting for the loop.
Having installed a lot of dishwashers I have never seen a machine not supplied with the U fitting.
I have however been called to find out why water was still being left in the dishwasher and it was usually because the hose was too low and allowing water to drain back into the machine, often when the sink was flushed and even worse when a garbage disposal unit was installed in the opposite bowl.

I don't believe it to be practicable for an air gap when connecting a dishwasher or clothes washing machine to a trapped standing wastepipe. The likelihood of siphonage is fairly negligible unless the hose is placed to deep in the pipe.There was a time where a coupled connection was applied, but I think this is now an outdated method.

Originally Posted by capt'ngrumpy

I don't believe it to be practicable for an air gap when connecting a dishwasher or clothes washing machine to a trapped standing wastepipe. The likelihood of siphonage is fairly negligible unless the hose is placed to deep in the pipe.There was a time where a coupled connection was applied, but I think this is now an outdated method.

the trap with a barb/barbs has an extended vertical section above the trap where the barbs are located. Clearance is built in the design.

Originally Posted by mic-d

the trap with a barb/barbs has an extended vertical section above the trap where the barbs are located. Clearance is built in the design.

Sorry. Fail to see your point. Talking about seperate connection to a standing waste, ie. dropping the drain hose into top of a 40 or 50mm vertical pipe, where the trap is at the base.

Originally Posted by Sterob

Our dishwasher makes very annoying noises ( as lots of other peoples do too ) when its running, as there is a direct line between the drain inlet and the sinks. Its like a pair of horns!

20240319_173436.jpg

I thought if I tapped into the drain line after the water seal(s) , that would solve our problem?
20240319_173443.jpg

Googling found lots of complaining but did not find anyone mention this as a solution......
It seems to make sense....have a water seal between the drain inlet and sink drains to stop the noise coming throught the sink!

Not sure if I would use two S bends or one at this stage....It depends on room under the sinks.
I can't think of any reason why this would not work. Am I missing something?

Can anyone definitvely say this will or will not work? Its alot of work finding fittings to discover I have been wasting my time....lol

Steve

You could substitute the 's' trap for a double nippled combination trap (available from bunnings) and connect the dishwasher hose to the lower nipple. This would displace the flow from dishwasher to below the weir of the trap and possibly soften if not nullify the gurgling noise. Provided the hose is looped to underside of the sink as previously mentioned, I don't see any problems with this approach.

I am not a plumber so you would have to confirm rules but I do not believe there is anything stopping you plumbing the dishwasher drain into a separate trapped connection. You may need this topped with an air admittance valve above the trap or there may be nothing stopping you from leaving it open.

Check with your plumber first.

Another option that may improve the situation is a remote trap further away from the sinks:
PK945 Spazio Plumbing Kit 3B
This also improves under sink storage in most cases.

Originally Posted by capt'ngrumpy

I don't believe it to be practicable for an air gap when connecting a dishwasher or clothes washing machine to a trapped standing wastepipe. The likelihood of siphonage is fairly negligible unless the hose is placed to deep in the pipe.There was a time where a coupled connection was applied, but I think this is now an outdated method.

What you believe and the AU Standards are 2 totally different things.
A coupled connection (totally sealed) causes siphonage where as a tundish is allowing air to be admitted to the pipe/trap as required in the Au Standards.
Of course you can hook the WM/DW drain pipe into the waste pipe as long as it finishes above the trap seal, that is a given.
The air gap is created by the fact the waste pipe is 40-50mm whereas the drain pipe from WM/DW is 25mm give or take.
FWIW there is a lot more to plumbing than asking the lady at Bunnings what you need then screwing/gluing a few pipes and fittings together.