Broke downstem need advice

You might need to use a little more water now that the downstem is shorter, but it'll work just fine

 

if your down stem breaks that's where you want it to break!

 

If the edges didnt shatter, you can try gluing them together with food-grade water soluble adhesive.
If that is not possible, just add a bit extra water in your bong and it will work just fine, albeit losing some of the diffusion the holes at the end provided.
Alternatively, buying a new downstem is not a large expense, you can get a high quality one for a few £.

A couple of budget options :
- Black Leaf - Inside-Cut Shower Head Perc Diffuser Downstem | Grasscity
- Black Leaf - 4-Arm Diffuser Downstem | Grasscity