Trying to get rid of an airlock

[Dark Eyes]

Every year or so, I seem to need to clear the gunk out of my kitchen sink waste pipes, which also take the waste feeds from the washing machine and dishwasher (see attached photos), which I do, after advice from a plumber, by removing the trap under the sink and sucking out the water and gunk with a Vax (whilst blocking off the washing machine waste pipe behind the cupboard).
It works, and when everything is connected back up, the sink drains at an acceptable rate, and the washing machine doesn't cause the waste pipe to overflow when draining.
However, this year, I have done exactly the same thing, but I now have an airlock somewhere past the trap, as the sink drains really slowly, and it burps for a while after it has finally cleared. I have removed and reattached the trap 3 times to see if I can clear it, but it stubbornly remains. If I release the connector on the horizontal pipe leading to the back of the cupboard, air hisses, water drips, and the sink drains quickly; but as soon as I tighten it back up, the air lock returns.
Does anybody have a suggestion as to how I might clear it permanently?

 

[rpm]

Please fit jubilee clips to the washing m/c hose before it disconnects and floods the floor with messy water
Have you tried snaking it?

 

[king of pipes]

Your problem is your waste pipework is having to cope with to much waste going down it washing machine , dishwasher, and kitchen sink waste all depositing debris into the pipe run and eventually blocking it how long is this run to drain ? over 3m - you could use a chemical digestant to clean the pipe but be aware these are often acid based , I favour a more gentle way washing soda add it to your washing machine detergent tray and dishwasher if you wish and set the washing machine program to the hottest setting this not only cleans your washing machine it often breaks down and flushes through any debris keeping pipes clear do this regularly to keep things flowing . Regards kop

 

[Dark Eyes]

This morning, I decided to 'Vax' it again via the horizontal pipe after the trap, and there was a thumb sized lump of clotted washing powder in the grey water. After connecting it all back up, the sink was draining freely with no siphoning or prolonged burping, so I ran the washing machine and as soon as it started draining the vertical waste pipe started overflowing...
I then removed the back of the cupboard, and undid the trap to see if it was clogged, but it was really clean, so I decided to 'snake and Vax' the waste pipe from that entry point, and although there were no noticeable lumps in the grey water, the washing machine is now draining freely as well.
How long it will last, I don't know, we switched to washing powder about a year ago, as I was told that the liquids were causing the pipe to gunk up and get blocked, but the powder seems to be far worse, as I have had to 'Vax' the pipe about 3 times in the past 6 months.
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Please fit jubilee clips to the washing m/c hose before it disconnects and floods the floor with messy water

The grey hose on the right is the dishwasher's, and it has been like that for at least the past 8 years, however, I have taken your advice and now secured it with a jubilee clip, although knowing my luck, that will have disturbed it and it will probably come off the next time I run the dishwasher.

 

[centralheatking]

In my own domestic experience and customers the recent availability of green low
temperature washing powders etc for washing machines and dishwashers has resulted in
a greater number of blocked and restricted small bore waste pipes...the emulsified waste
at low temperature re forms quickly before it gets to the 4 inch drains, and will block normally well performing 11/2 waste. After all detergents are only mini magnetic particles which attract the dirt and carry it away and they work best at higher temperatures. We are looking at a new drain and jetting business for one of my sons...as he has a driving licence now...we have registered
Mr Poo....'blocked drain or loo, what do you do, pick up your phone and call Mr Poo'
centralheatking

 

[Dark Eyes]

temperature washing powders etc for washing machines and dishwashers has resulted in
a greater number of blocked and restricted small bore waste pipes

Do you think the liquids are any less likely to cause clogging, if we mainly wash at 30/40'C ?
It seems that the monthly 60'C wash seemed to have keep the pipe clearer for longer with the liquid.

 

[centralheatking]

Do you think the liquids are any less likely to cause clogging, if we mainly wash at 30/40'C ?
It seems that the monthly 60'C wash seemed to have keep the pipe clearer for longer with the liquid.

Yes that is my opinion, low temp detergents re form much more quickly and cause premature blockages. Maybe the answer is to run every so many washes at higher temperature. centralheatking

 

[rpm]

What's this re forming mini magnetic you speak of Rob
For me liquid or gel tabs are better and plenty of water of course.
I've just brought a super doper water saving wash machine but the outlet is only 2ft away

 

[Stevenb-Npton]

I hate the washing powder especially as people seem to be using much cooler washes now, it seems to produce that powder gunk. liquid washing is the way forward.

 

[centralheatking]

I hate the washing powder especially as people seem to be using much cooler washes now, it seems to produce that powder gunk. liquid washing is the way forward.

agree, we have gone to properties which have had no probs ever or for years and when they get it sorted its hard lumps of reformed detergent powder....we know the difference between poo, fat and
detergent its quite obvious ...low temp powder causes endless trouble...my sons make money out of it so its happy days
chking