I have installed the dishwasher and washing machine waste with one of those twin entry things as the top with a breather hole connected to a stand pipe u-bend and exit out thro wall and down to drain.
Now the twin entry is quite high, level with the top of the machines and the U-bend is approx half way down
The Q is, could I be getting any waste up say from the washing machine through to the dishwasher becase the stand pipe is too short ? (this is a guess) Its just the crockery is coming out after a finished cycle and it smells funny, (not nice)
Make sure you haven't pushed the waste hoses to far down the pipes as this can cause syphoning back to the appliance. The waste hoses need only be half way down the stand pipes at most, and should have an air gap around them to help stop any syphon action.
They are hoseclipped onto tapered connectins at the top, like i say the standpipe and top twin connnector is purpose built for the job. My concern is the length of standpipe.
If both waste hoses are to close together without separation into the stand pipe, then this can cause one appliance to force dirty water back to the other appliance. Two appliances with pumped waste systems need to have separate stand pipes. If they don't, then the do run the risk of blowing dirty water into each other.
I don't know what type of waste system you have on this, but you say it is purpose made for the job. If the system you have is two tapered spouts connected to something like a TEE fitting on the stand pipe, then this needs to be fitted with one waste hose horizontal to the side branch of the TEE and the other vertical on the top of the TEE fitting. The shape of the TEE branch then stops waste water being forced into the other appliance.
If the TEE fitting has been installed on the horizontal with the branch on top, then the whole TEE fitting needs to have quite a angle to prevent water being forced back in to other appliance with the pressure of the pump action.
Can you show a picture or website for the twin waste outlet system you're using please?
NO way Hossay!!! The waste hoses are directly facing each other at the top of the stand pipe. Pumped water will only flow passed the top of the vertical pipe and down the waste hose of the other appliance. This is no good for two appliances Vass. You have the twin inlet with, what should be a separator fin down the middle of the fitting, but they don't work, as you've already found out. They are OK on a small two outlet basin system where the water is not under pressure, but they don't work on pumped waste systems.
I'd much rather you squeezed the two black rubber bits of the waste hoses into the top of the stand pipe on their own, rather than use that fitting. In fact, I'm going to tell you to squeeze the two black rubber hose ends into the top of the stand pipe, and press the hoses down as far as the middle of the pipe if you can.
You'll also need something to hold the stand pipe upright when in use, as the weight of the water under pressure from the pumps may cause the U to twist around and empty its contents on to the floor. I see a copper pipe horizontal near the top of the stand pipe, so you might be able to tie a string around the stand pipe and around the just to give some needed support. A proper pipe clip around the vertical stand pipe would be much better though.
But its a special one with a vertical divider in the top with a breather hole so there's no direct passage from one pipe to the other Is this really useless then ?
The breather valve on these things are OK for a trickle flow of water from a small sink or basin, but they are rubbish at opening quickly enough when the force of pumped water is applied to them. By the time the breather valve has opened to allow air to be sucked in, half the water has already gone passed the vacuum point at the sealed twin fitting and gone down the other waste hose.
You don't need the breather valve when you install a U shaped water trap anyway, so the air inlet part of the fitting can be removed. The stand pipe is just large enough to allow two waste hoses to be gently squeezed in to it, and allow enough of an air gap to let the pumped water flow easily and without creating a vacuum on the other hose.
Anything flowing back in to the waste hose can cause it to smell, and you may actually have been sucking some water back up from the U trap before the breather valve on the fitting had opened. So there's telling what you may have sucked back in to the appliances.
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