Kitchen waste - compression vs push fit for outside? Which pipe? And do I need an AAV?

[Plumb Line]

Hi all

Sorry for the long title but thought best to bung all these questions together.

I'll be fitting a new kitchen sink soon and am unsure on the following...

1. Compression vs Push Fit for outside? I know solvent weld is the preferred and professional choice, but I'd really like to be able to dismantle every so often and clean out the pipes...

2. Which pipe for outside? If I'm using push fit then I guess the answer is obvious! but if using compression I've read I can use either type of pipe. Which stands up best to the elements? And do both types need painting (have read various answers on that question)?

3. Do I need an AAV valve? I'm totally confused as to when they are/aren't needed. For context, the kitchen sink is not connected to any other wastes. And it is open ended , i.e. the open end of the pipe sits just inside the drain cover grate. EDIT - I should add. There is no AAV in the existing set up. However, in case it matters, I will be going from a sink and a half to a single sink, and I'll be adding a dishwasher where does was none before.

Any help would be much appreciated.

Many thanks for reading 🙂

 

[Last Plumber]

1: Doesn't matter
2: Doesn't matter
3: Not if it is a short run.

That's my response to the image I have inside my head, going off your descriptions.

Hope it helps.
EDIT:- Make sure the fall is right and it is clipped properly. I would - as you pointed out - use solvent or maybe pushfit but it is your choice really. I have never painted it and never heard of a problem. The only thing I have noticed is that dark colours like black will bleach in the sun but it doesn't seem to effect their quality in the life span. Some plastics are not meant for external use due to UV etc but the stuff you are using is designed to be external and internal.

 

[Plumb Line]

Many thanks for the reply.

OK, that's good then. The more I have read and asked about on the subject, the more I find people saying to use solvent weld and nothing else, all pros use solvent weld, etc. When you say it doesn't matter, do you mean the choice between all 3? Or just that it doesn't matter which I choose between push fit and compression, but that ultimately solvent weld is best?

On a different but related matter, I've been advised to avoid using a sink trap with stubby connector for dishwasher (before the U bend trap), as with these you hear all the water discharges via the sink plug hole. Rather, it is better to use a standpipe for the dishwasher and then connect the sink waste and standpipe before exiting the building.

That all makes sense to me, but wondered what anyone on this forum thinks?

Thanks again

 

[RBG]

was just about to post and last plumber had said exactly what I was going to say.

There is this link that explains about pipe types - Push-Fit or Solvent Weld - which waste pipe system is better? - https://www.jdpipes.co.uk/knowledge/above-ground/push-fit-vs-solvent-weld.html

If you wanted some more info

I normally only use solvent weld and the timesI have used outside never had a problem. Osama pipe have one they claim is uv resistant etc so suitable for outside. The others I don’t

If you want to clean out them maybe be add access points / ridding points so you don’t have to take completely apart.

 

[RBG]

Many thanks for the reply.

OK, that's good then. The more I have read and asked about on the subject, the more I find people saying to use solvent weld and nothing else, all pros use solvent weld, etc. When you say it doesn't matter, do you mean the choice between all 3? Or just that it doesn't matter which I choose between push fit and compression, but that ultimately solvent weld is best?

Pro's use solvent weld as more permanent, less likely for seals to go over time (long time) and also when under things like floors etc that is useful. SW is also less bulky and neater and the fittings are better valve. Ultimately, all 3 will work satisfactorily. It is easier to use push fit and compression if you aren't used to SW as you can redo easily.

On a different but related matter, I've been advised to avoid using a sink trap with stubby connector for dishwasher (before the U bend trap), as with these you hear all the water discharges via the sink plug hole. Rather, it is better to use a standpipe for the dishwasher and then connect the sink waste and standpipe before exiting the building.

That all makes sense to me, but wondered what anyone on this forum thinks?

Thanks again

You can hear the noise in the plug trap. I guess that is a personal choice as to if it annoys you.If you can fit a standpipe, then this is a solution to it but do you have the room, the correct fall for it, does it make the pipe work harder and more complicated?

 

[Last Plumber]

On a different but related matter, I've been advised to avoid using a sink trap with stubby connector for dishwasher (before the U bend trap), as with these you hear all the water discharges via the sink plug hole. Rather, it is better to use a standpipe for the dishwasher and then connect the sink waste and standpipe before exiting the building.

It is always best practice to use a separate waste for things if you can. The spigot connection will do if you cannot get a stand pipe in. It will make a bit of noise but I doubt it will bother anyone. I have never heard of anyone being bothered by noise and when I have connected to those in the past and tested the empty process of a washing machine, I can't say as I remember thinking anything negative. I suppose if the waste blocked after the trap or if the trap blocked, your machine would empty and fill the sink. It could possibly overflow? That is the only real issue I can think might worry me but I have never seen that happen.

If for example someone poured fat into a sink waste and it set? That would block the trap and the overflow from the sink wouldn't it. Worst case scenario!

 

[Plumb Line]

Just returning to say thanks for the replies and help.

I'm going to stick with the spigot connection as I think it will just be easier given the space available, etc. I'm pretty careful on what I put down the sink, and I also take apart and clean the undersink pipework once in a while, so hopefully I'll avoid any of those potential nightmare scenarios!

Cheers