Can I install washing machine and dishwasher to one trap?

Thank you for your time and advice in advance.

Hi, I would like to install dishwasher and laundry.
Current trap has one nipple, so I am thinking to install Holman trap with 2 nipples as per attached image. Will this work? Any advice would be appreciated .

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EricL

Hello @mu1u2b

Welcome to the Bunnings Workshop community. It's sensational to have you join us, and thanks for sharing your question about your under-sink trap.

Please note that replacing the trap is considered plumbing work, and I therefore suggest engaging the services of a licensed plumber. The replacement will be done to code and will come with a guarantee with it.

In regards to using both inlets, it is definitely possible. Please note however that you can only use one machine at a time and and they must not be used at the same time as there is a possibility of the trap getting overwhelmed.

Here is a handy step-by-step guide: How to connect a dishwasher.

If you have any other questions we can help with, please let us know.

Eric

mu1u2b

Hi Eric,

Thank you for your kind and valuable advice.

I am keen to have both installed and be able to use at the same time. How about connecting a dishwasher to a current one inlet trap setting and installing laundry drain on the sink? Will this way work or make any difference? Could you think of any

way I could use both machines at the same time? Thank you again Eric and have a good day.

JacobZ

Hi @mu1u2b,

I'd also like to welcome you to the Bunnings Workshop community; it is fantastic to have you with us.

I'm not aware of a reason that you couldn't have the washing machine draining directly into the sink, but it is not an ideal setup.

I would suggest contacting a plumber to quote on installing the dual-inlet trap on your behalf. They will be able to determine the feasibility of using the dual-inlet trap and recommend any changes needed for this setup to work effectively.

Allow me to tag some of our helpful members to see if they have any advice, @PlumbMaster-Zee, @DIYGnome, @Dave-1.

Let me know if you have any further questions.

Jacob

DIYGnome

Hello @mu1u2b 😊

I would have to concur with both @EricL & @JacobZ a second trap is warranted if concurrent use is the primary concern, pipes are like roadways and like our road system everything is good till 5pm when people knock off work and Parents are ferrying their Children to/from after School activities... absolute bedlam 🤣

Is there Plumbing in an adjacent area? 🤔

Have you considered running the water output from one appliance to outside to feed a grey water system (for the Garden)? 🤔

Dave-1

Afternoon @mu1u2b

Thinking of the quantity of waste water coming through the two inlets plus the sink itself makes me head towards @EricL , @JacobZ and @DIYGnome are suggesting that it may be an idea to have a plumber look at what can be done. Having all three dump water at the same time will surely cause a backup of the drain. Also having the lundry water exit into the laundry sink may not have the same exit capacity as straight into the drain, causing the sink to fill before it can drain away.

Dave

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