Question: I've purchased a dishwasher supposedly with exact same dimensions as the previous however swapping out hasn't been as straightforward as I imagined. The issue is a waste pipe, ever so slightly in the way and preventing the dishwasher from a flush fitting. There's about 25mm in it. The connector pipe appears to have an unnecessary T fitting (see pic). I was thinking about swapping out the connector and have 2 questions:

1) Is that T unnecessary? Or is it some type of non-return valve

2) If it's solvent welded I've read that I'll have to saw the pipe off. If so do I cut, insert a new length of pipe and then solvent weld with 2 40mm Straight Coupler's?

Thanks! 

![Waste pipe connector](https://i.stack.imgur.com/3bWnY.jpg)

Answer: 
That kind of T-connection low down suggests that it joins the wastes from two P-traps.

It is probably more usual for dishwashers to connect above the P-trap of an adjacent sink.

![enter image description here](https://i.stack.imgur.com/UxhWD.jpg)  

An "appliance P-trap", the tapered nozzle on the left is to connect the outlet hose from an appliance such as a dishwasher.

You can also get a "standpipe appliance trap"

![enter image description here](https://i.stack.imgur.com/pZXJb.jpg)  

I've not used this type but your appliance hose would be hooked into the top.

---

If you can remove one of the outlets that your T-joint combines then you might be able to plan a new layout for the waste pipes that provides more space for your appliance.

It isn't clear to me from your photo, exactly what the problem is and what exactly feed the two inputs to that T-join.

In principle you can cut through the pipes and push on a new solvent-weld (or push-fit or compression fitting) joint. But you need enough pipe remaining after the cut to fit into the coupling. The more times you cut and remake these solvent-weld joints the less and less pipe you have to work with. 

As you suggest, if there is nothing using the vertical waste pipe above the T, you could cut out the T and cut back the existing pipe far enough to fit a new section of the same type of ABS pipe with two straight couplings.
The plumbing code (UPC or IRC) doesn't allow the use of a sanitary tee in a horizontal position. It can only be used vertically. Your supposed to have a long sweep or a wye-and-⅛ combo where that tee is.

> 
> Uniform Plumbing Code
> =====================
> 
> 
> Chpater 7 Sanitary Drainage
> ---------------------------
> 
> 
> **706.0 Changes in Direction of Drainage Flow**
> 
> 
> **706.4** Vertical drainage lines connecting with horizontal
> drainage lines shall enter through forty-five (45) degree
> (0.79 rad) wye branches, combination wye and one-eighth
> (1/8) bend branches, or other approved fittings of
> equivalent sweep. Sixty (60) degree (1.05 rad) branches or
> offsets may be used only when installed in a true vertical
> position.
> 
> 
> 

Depending on what it is draining, you might be able to reduce the size of the pipe going to the left.

The vertical goes somewhere. Where does it go?