# Forum Home Renovation Plumbing  washing machine draining into sink pipe

## turando

What is the best way to drain water from the washing machine into the pipe from the laundry sink? Is there an attachment we can buy? We used to drain into the sink directly but I've just put a new sink in and bench so that won't work now. Photo shows current draining which is the pipe is open so can't use the sink yet.

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## John2b

Some machines need to have the waste pipe open to air to prevent syphoning back. If that is the case with your machine you have to be careful to prevent syphoning. Is it front or top load? The water level in a top load is much higher and the outlet must be higher than the maximum level in the tub. If it is a front load machine, you might be able to use the barb connection above the trap just under the bowl connector. The barb connection will need to be drilled out to allow water through. Be very careful if you drill this as it is easy to crack open the trap which can be brittle. Check in the user manual for the machine about using the barb connection. You'll probably need a hose clamp if you can use the barb, to prevent leaks when the machine is pumping out.

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## johnc

Yes, just drill out the nipple with a 12 or 13mm drill. You will need a hose clamp, slide clamp onto hose, push hose on nipple, tighten, simples! Hose will vent up through the sink waste anyway, there should be no risk of a syphon.

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## turando

Thankyou both.  
It's a new front load (bosch).  
I will try out the drill and hose clamp. I have spare one of those pipe connections so if i do break it can use the other one.

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## Bedford

Those nipples are really for dishwashers, washing machines pump a lot more water faster and really shouldn't be restricted.

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## turando

is there an alternative pipe i can get that would work for both sink and washing machine without restricting?

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## Bedford

I've seen them done with a double bowl connector https://www.google.com.au/shopping/p...E,gclsrc:aw.ds reduce it down to 40mm, make the 40mm as high as you can leaving enough room to drop the WM drain into it. 
You would also need to support it.

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## droog

> Those nipples are really for dishwashers, washing machines pump a lot more water faster and really shouldn't be restricted.

  Check the user manual, a number of washing machine manufacturers detail connection via a nipple the same as dishwashers. Bosch do have it in some of their manuals but I don’t know which model you have.

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## turando

I have the WAW28460AU  https://www.appliancesonline.com.au/...ser-Manual.pdf is the manual 
It mentions on page 40 about drainage into a siphon - is that dishwasher thing a siphon?

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## droog

Happens to be the same manual I checked, yep they refer to the connection as a siphon. 
Just be sure to drill the entire diameter of the connection out, don’t just put a 10mm hole through it, they are usually about 13mm or just use a file or other tool to open it out to the full diameter.

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## John2b

The Bosch washer user manual linked shows the drain hose connected like a dishwasher to the barb connection above the trough waste trap  on page 38. The manual also recommends using a hose clamp as suggested above.

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## Marc

Newer machines all connect like a dishwasher not with the old upside down U shaped hose.
Another difference with this machine (according to the manual) is that the door does "Clack" when closing not click ... go figure.  :Smilie:

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## Bedford

> Newer machines all connect like a dishwasher not with the old upside down U shaped hose.

  You mean like the OP's? :Biggrin:     

>

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## Marc

Ha ha, yes Bedford, I saw that, obviously that is an older machine, however short of changing the sink the Op needs to pump into the S trap somehow. My point is that if the smallish dishwasher connection is Ok for new machines, it should be ok for older ones, just a matter of finding the right connections. 
My suggestion is to call a plumber.

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## John2b

The plastic saddle is supplied with Bosch washing machines to clip on the outlet hose where a trap barb for connection is not available.

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## YoungBolt

I spoke to a plumber about directly connected the outlet pipe to a spigot connecton like we do with the dishwasher, and he outright refused to do it and has never done it that way. He believes that there's too much water flow for the standard dishwasher spigot to properly drain away and the pipe needs to be open to allow air for the suds to dissipate.  
He installed an open pipe connected above the S trap. It's been like this for about two years without any trouble.

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## phild01

> I spoke to a plumber about directly connected the outlet pipe to a spigot connecton like we do with the dishwasher, and he outright refused to do it and has never done it that way. He believes that there's too much water flow for the standard dishwasher spigot to properly drain away and the pipe needs to be open to allow air for the suds to dissipate.  
> He installed an open pipe connected above the S trap. It's been like this for about two years without any trouble.

   :2thumbsup:

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## cyclic

> Newer machines all connect like a dishwasher not with the old upside down U shaped hose.
> Another difference with this machine (according to the manual) is that the door does "Clack" when closing not click ... go figure.

  The upside down u shaped plastic thingy is for fixing the hose up high under the bench top to stop siphonage.

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## cyclic

> I spoke to a plumber about directly connected the outlet pipe to a spigot connecton like we do with the dishwasher, and he outright refused to do it and has never done it that way. He believes that there's too much water flow for the standard dishwasher spigot to properly drain away and the pipe needs to be open to allow air for the suds to dissipate.  
> He installed an open pipe connected above the S trap. It's been like this for about two years without any trouble.

  Your plumber is far from the brightest bulb in the lighting circuit when you consider if you were to fill the laundry tub with water then pull the plug, the water would pour out the top of the 40 mm pipe cause it is close to the base of the tub line. 
Try it if you don't believe me. 
Any connection like that should be as high as possible up under the bench top.

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## phild01

> Your plumber is far from the brightest bulb in the lighting circuit when you consider if you were to fill the laundry tub with water then pull the plug, the water would pour out the top of the 40 mm pipe cause it is close to the base of the tub line. 
> Try it if you don't believe me.

  Be interesting to know the outcome but if there was a blockage then that would spell certain  disaster for the cabinet.

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## Marc

It is fairly obvious that the prediction cyclic is making has 100% probability. 
The washing machine pipe needs to be fitted to the trap with a clamp not sitting lose. You can do it that way if you hook it on the sink edge or hook the hose to the outside window and let it run into the neighbours property.
Clamp the hose to the spigot for dishwasher or otherwise, buy a proper connection like this one  https://www.ebay.com.au/itm/Kitchen-...-/121854915712

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## YoungBolt

> Your plumber is far from the brightest bulb in the lighting circuit when you consider if you were to fill the laundry tub with water then pull the plug, the water would pour out the top of the 40 mm pipe cause it is close to the base of the tub line. 
> Try it if you don't believe me. 
> Any connection like that should be as high as possible up under the bench top.

  He was newly qualified plumber too! He got his cert about 2 months before old mate installed it. 
I'm curious and scared now! 
I might have to get a coupling from bunnings and make it a bit higher. 
I lost the clamp for the washing machine outlet line so he couldn't install it, but he shoved the outline line a good length into the pipe. 
I'll try and see if bunnings sells a clamp or call the manufacturer for a spare part.

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## cyclic

> He was newly qualified plumber too! He got his cert about 2 months before old mate installed it. 
> I'm curious and scared now! 
> I might have to get a coupling from bunnings and make it a bit higher. 
> I lost the clamp for the washing machine outlet line so he couldn't install it, but he shoved the outline line a good length into the pipe. 
> I'll try and see if bunnings sells a clamp or call the manufacturer for a spare part.

  Don't be scared, it will only occur as I said if the tub is full and the plug is pulled. 
Not sure what clamp you are referring to ?? 
A plumbing inspector would fail the existing connection but only because it needs to be higher to stop overflow, so if you want you can get a 40 mm socket, pvc glue, and some 40 mm pipe and simply raise it as high as possible while still allowing the wash machine hose to fit  
I have never seen the fitting Marc shows in #21 but it is a good idea..

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## phild01

I'd still be interested to see if it did overflow, as the exit speed of the outrush through the trap might be fast enough to beat the rise in that open pipe.
Go on Youngbolt, give it a go :Biggrin:

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## YoungBolt

Haha I should video it! My only concern is catching the water!  
Came to help someone else, ended up needing help for myself  :Rofl:   
Yeah i'll get a slip coupling and bit of hose to lift up the height of the opening to the pipe. Easy stuff.

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## Marc

Cyclic, in a pinch you can make that T connection fairly easily. 
YB, if it overflows, have a bag of rice handy to soak up the water  :Smilie:

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## YoungBolt

The misso aint home tonight, so when the cat's away, the mice will play!!  
I should be able to slightly unscrew the sink connections and move the pipe outwards from the cabinet.  
I'll have a few beers and then see what happens   :Biggrin2:

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## cyclic

> The misso aint home tonight, so when the cat's away, the mice will play!!  
> I should be able to slightly unscrew the sink connections and move the pipe outwards from the cabinet.  
> I'll have a few beers and then see what happens

  Tell her Marc assured you everything would be ok. 
If you fill the tub, pull the plug and get ready to wack the plug back in to stop the flow.

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## Uncle Bob

> I'll have a few beers and then see what happens

  That's the spirit!  :Smilie: 
If the starts to flow out the open section, bung the plug back in quick, or put your hand over it.

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## droog

> I'd still be interested to see if it did overflow, as the exit speed of the outrush through the trap might be fast enough to beat the rise in that open pipe

  It sure will if there are problems downstream in the pipework, have seen it when an ORG was buried in the garden.

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## Marc

> Tell her Marc assured you everything would be ok.

  On the contrary my friend. I said your prediction [ of doom ] is 100% correct. Guaranteed flood, if the tub is full and you pull the pug wide open. 
If you want to avoid flood and want to make a shoddy job, seal the hose to the pipe with duct tape, nice and tight. Job done! 
if on the other hand you want to make a bigger mess, pull the plug and start pumping with a plunger in the tub  :Rofl5:

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## phild01

Thinking about it more I wonder if any water will overflow as long as the draining is not impeded. In fact the pipe will have low pressure air in it thinking back on school science experiments.

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## Marc

You are correct, but the S trap will work against free flow, and if there is just that little bit of fluff in there ... start mopping quick before the missus comes back  :Smilie:

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## phild01

I don't think the s trap will be much of an impediment but venting might come into play further down the line.

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## YoungBolt

Sink is filling!

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## phild01

Maybe do it in increments. :Unsure:

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## YoungBolt

And the test is complete. Interesting outcome!! 
Can't say I don't commit!

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## phild01

Yay, looks like good plumbing (until if you get a blockage), did you look down the pipe at all to see any water. 
If you do it again put a freezer bag over it with elastic bands, you should see the bag getting sucked in.

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## Marc

Interesting ... now try the same as the washing machine pumps water in there at the same time ...

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## cyclic

> And the test is complete. Interesting outcome!! 
> Can't say I don't commit!

  YB, you get A for effort, but keep in mind you have a basket waste which I have found do not drain the same volume as a standard waste, so that will have a bearing on the outcome.
The law still applies that any open pipe in that situation must be above the overflow level of the fixture.
Remember the old laundry tubs with the by pass up to the bench top.

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## Marc

It worked great. I was wrong. 
It seems that the water going down the pipe sucks air as it goes down rather than finding it's level. Hydrodynamics as opposed to hydrostatics. The slow release of the sink seems to help, the column of water pulling down the S trap and beyond unimpeded, compensates the slow travel by sucking air through the side pipe. As long as the speed of the water down the pipe is faster than the rate of release of the sink, there will be low pressure in the side pipe and no danger. However if the flow is reduced in any way, like some fluff from the washing machine in the S trap, the sink water flow will be faster than the pipe flow and it will find it's way out the washing machine open pipe.
If the volume of water wanting to go down the pipe is more than the pipe can carry and the flow slows down ... like if the washing machine is draining and the sink is also draining, the pressure will no longer be negative and you have a flood. 
All you need to do is tape the washer hose to the PVC pipe.

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## droog

> the pipe sucks air as it goes down

  And that’s all good when there are no issues, but when something else is wrong downstream the open pipe is a perfect place for it to burp it’s contents into the cupboard.

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## Gooner

> I spoke to a plumber about directly connected the outlet pipe to a spigot connecton like we do with the dishwasher, and he outright refused to do it and has never done it that way. He believes that there's too much water flow for the standard dishwasher spigot to properly drain away and the pipe needs to be open to allow air for the suds to dissipate.  
> He installed an open pipe connected above the S trap. It's been like this for about two years without any trouble.

  I don't get this thread. If you have the right drain pipe connection for the washing machine, the washing machine pipe inner diameter is about the same as the inner diameter of the pipe connection. I.e. about 20mm. So..... what's the problem? Yes, if you're going to get a 20mm washing machine pipe to connect to a 12mm drain connection then this is obviously not ideal...... so just change the trap to the right type. Why go for the arrangement shown above? Am I missing something here? 
Going back to the original post, you can see the pipe and drain pipe diameter is about the same. Drill it out fully, hose clamp it in, and be done with it. (??)

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## droog

> Am I missing something here?

  While we know that the OP’s machine is ok we don’t know the details of the picture referred too. Some manufacturers do not support connection to a spigot, doing so will void the warranty of the machine.

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## YoungBolt

To all those playing at home - this is what I ended up installing to rectify what my newbie plumber installed 
checked my washing machines handbook and it stated that a drain pipe in the only option for the outlet hose without running into a sink.
also stated it needs to be minimum height of 600mm, ideal 650mm.
managed to install a 620mm height drainpipe 
Have run the washing machine with a full load. Cabinet is still dry!

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## intertd6

There's really no need to be re inventing the wheel, the spigot under the sink will take the washing machine outlet, it's virtually the same ID as the spigot. The last few washing machines I've had have been connected to the spigot , floor mounted  front loaders & there was no problems with siphoning.
inter

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## alexyeo

Interesting setup YoungBolt, I may refer to this setup for what I am trying to achieve below. 
I have a standard laundry tub with a 40mm washing machine spigot (located around 100 mm below the bottom of the tub and approx. 400mm above floor level) that elbows up to a hole in the top of the tub -- this is where the current washing machine outlet is inserted (front loader with pumped outlet). 
I want to add another washing machine on the other side of the tub. It is a gravity-draining front loader from Japan, that usually plugs into a drain waste beneath the washing machine in normal installation setups. I want to connect this to the waste under the tub, but don't want it leaking or have the other washing machine back flowing into this one. 
I am going to make a pedestal up for the washing machine to sit on around 600mm above the floor. The question is how to setup the drain properly. The existing tub is rarely ever used/filled, but I guess I should keep in mind the risks involved with that possibility. 
Options:
- should I put in a 40 mm tee piece similar to YoungBolt beneath the existing 40 mm spigot, so that the new washing machine can drain into?
- should I have the new 40 mm tee piece above the existing 40 mm spigot?
- should I have the new 40 mm tee piece as low as possible in the cabinet but above the trap (even if I have to lower the position of the trap), and the new washing machine pedestal as high as possible (practically, high enough to reach the buttons at the back of the machine --- a 600 mm pedestal will position the top of the washing machine at around 1.6m high already). 
In either case, like like YoungBolt's setup, it looks like I will need to extend the tee piece 90degrees vertically as high as possible, keeping it below the lowest point of the washing machine to ensure that gravity drains the water properly. 
Any advice appreciated, thanks in advance.

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