Getting shower water out of the house for reuse

Greetings!  I have been lurking on the forums for a while but finally have a question that will benefit from collective knowledge
We have been doing the bucket in the shower routine to save our shower warm up water for reuse watering plants, which is great.  However, hauling a bucket of water through the house to get to the door where the garden is accessible is less than ideal.  It takes time and it's heavy and annoying.  The partner did some internet research but we haven't been able to find any easy solutions for getting it from the shower directly out to the garden.  We were thinking the easiest thing would be to put some sort of sluice or port in the wall of the shower so we could just empty the bucket from there but no one seems to have done anything like this.  We have a tiny high up shower window that is not really reachable and a window in the bedroom with the shower in question but they both have screens on them and screens are important to keep intact.  
Any thoughts?

Hi Lacy,
What sort of shower enclosure do you have? My first thought would be to simply use the drain that is already there. but re-route the drain pipe into some sort of out-door water tank instead of the normal septic. Then if the tank is higher than the garden, you can just connect a hose and use gravity. Even if you needed a small hand pump to get the water to the garden after, I feel like it would be easier than hauling it through the house :)

Matt,
The house is on a concrete slab and all the drains are set into it, so I can't get at the drain in any meaningful way.  It has to be collected between the showerhead and the drain, which is why we have just been doing buckets for warmup water.

Hi, Lacey that is a great question.  

Most drains in homes combine the black and grey water when leaving the house so there might be several other options.

As you have suggested a port through the wall of the house. This port could be a piece of PVP port that a hose can be attached to on either side of the house (inside then on the outside).

If I were doing this, I would plug the drain to catch the water in the shower pan rather than a bucket.  As I took my shower the water pump would pull the water through the hose directly to the hose outside where I wanted to water.

I hope this is something that would work for you.

A water pump will help move the water outside.