ᐅ Trap – Flush water drains extremely slowly after replacement

Hello everyone,

I’m not building a house, but since I couldn’t find a better forum, I hope you can still help me.

Here’s the situation in the kitchen:
- I replaced the sink and the trap
- Since then, the water drains very slowly (a full basin takes 2-3 hours to empty)
- If water is poured directly into the wall drain, it drains normally
- If the trap is not connected to the wall but drains into a bucket, the water also drains normally
- Before the renovation, everything worked perfectly

What am I overlooking?

Thank you very much for your help!

You are overlooking your strange construction; as long as water cannot flow uphill, nothing will change.

The height of the siphon should be the pipe diameter plus 1cm (0.4 inches).

Thank you for your reply. At which point would the water need to flow upward?

It’s possible that I’m misunderstanding the function of a trap. I’ve marked the water level in blue. The level inside the trap is equal, then water is supplied from the basin, causing the level to rise until it reaches the overflow on the right, and the water flows downwards into the wall drain.

If the water were supposed to flow upward anywhere, no water would come out when I disconnect the system at the red-marked line. But it does. The water also drains normally when I pour it directly into the wall drain. So clogging can be ruled out.

I suspect it is also due to the narrow cross-section of the shallow trap at the upper part, which results in insufficient pressure to overcome the height of the trap.

This is not a DIY construction but prefabricated parts sold by a well-known furniture store, assembled according to instructions. If it didn’t work due to the cross-sections, there would definitely be more complaints online, and the siphon would no longer be available.

I’m afraid my only option left is to buy a new one with a proper system.

Sorry, but even if a furniture store is selling it, it doesn’t look right.

What brand or manufacturer is indicated on it?