I am planning on having access to the back of the tank. There is going to be a 90cm gap from the wall to the tank and it will be closed off with a door. It might be a bit of a struggle but I think I should be able to reach the bottom. My arm is about 75cm long and once I add an inch or two of sand and account for the water being slightly lower than the top of the tank it should be ok. I just don't like the look of a 2 foot deep tank when it will be around 10-12 foot long, it looks too narrow.
Also, We had the tender appointment for our house a few weeks back and we were told that our concrete slab should be able to hold the weight of the tank with no issues as long as the weight is spread evenly. It will be a H2 class waffle slab. I am still not too sure as it will weigh around 3 tonnes so will probably get a second opinion before installing the tank, however the engineer said it will be ok after I questioned it 2 or 3 times.
They have advised us also that the capped waste point cannot be put into the cavity behind the wall, it will have to go in the floor so I will put it in the corner as you can see in the diagram. I also need to decide where to put the water point and dedicated power point. I will either put them in the wall in the corner next to the capped waste point, or in the wall in the middle of the tank. Any opinions? Ideally I do not want to have cords all over the place behind the tank as I will be going behind the tank for maintenance which is why I am thinking of maybe putting them in the corner.