Blocked sink - installation issue?

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Hi all

In the last few days, our kitchen sink and garbage disposal has started to block up. After doing the usual sink unblocking steps (see below) we are questioning the original installation - specifically the joint highlighted in red box on attached image.

IMG_3948.JPG


Should the outflow from the sink feed back into the garbage disposal?
Should some of the outflow from the garbage disposal flow back up to the sink?

Since the installation five years ago (not in touch with builder who supplied plumber), we did wonder why the garbage disposal chamber needs more cleaning that we expected and why our son complained of a strong smell in the kitchen each morning.

Appreciate your views on whether the joint highlighted has been fitted incorrectly (we suspect the wrong way round) and if so how much a plumber may charge for this and to clear any remaining blockage.

For context, here is what we have done so far to address blockage.

Mr Muscle, OneShot and plunging has seen us through Christmas. On the attached image, we took off the bends with a green line and cleaned them. And used a Draper drain unblocker (auger) along the pipe with blue line getting as far as the bend going into the back. This has got us back to almost where we were before.

Thank you

Jerry
 
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1. That swept Tee should be the other way round, pointing the sink outlet towards the pipe that goes through the back of the cabinet, and presumably to drain.
2. However, not sure that would cause a frequent blockage. The waste should flow through to drain albeit after backing up a little.
3. No one can tell you how much to permanently cure the recurring blockage:
3a. Might be cleared by reversing swept Tee, in which case probably 1 to 2 hours labour and the cost of bits - £100 to £150 in London.
3b. If further investigation / changes required - no telling the cost, but unlikely to be more than £200 - again, London.
 
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The swept tee is installed the wrong way around, the swept section should point towards the outflow through the cabinet back.

The horizontal pipe could have a little more fall on it as the sink waste water could also be overwhelming the Waste Disposal's (WD) trap too.

The trap for the sink should really be set a bit higher up and then the outflow from the trap should tee into the the top of the horizontal pipe coming from the WD to the outflow. That would reduce the risk of backflow into the sink from the pumped waste disposal and dishwasher.

Change that sink waste/trap setup for a more robust make - McAlpine would be my recommendation.

With a WD, sink and 2 machine outlets on the same run then it all really needs regularly cleaned and flushed with boiling water and bicarb or stripped down, to keep everything clean.
 
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As above, and be very careful taking anything apart now you've used 'One shot'. That stuff is evil and will burn through skin and tissue in seconds, please warn anyone else who looks at this that you've used chemicals.

Ideally needs upgrading to 50mm pipework where the sink tee joins, given the amount of possible discharges, and the waste disposal unit on the run.
 
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Totally missed that part ... a most important shout by @Hugh Jaleak -

'One shot'

One shot is a restricted product and as such shouldn't be sold to anyone outside the industry due to it being a concentrated acid. Unfortunately it is all too easily obtained.

Make sure the pipework is completely flushed with copious amounts of cold water before attempting anything on it. Even then I'd still probably use gloves and glasses.
 
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