Water coming up thru sink etc?

A few days ago after flushing the loo, the water would fill up the bowl as if there was a blockage and then drain out really slowly. After it reached the normal level it would carry on draining below the normal level as if the water was being sucked out through the u-bend.

Today the washing machine started to drain and water came back up through the sink next the washing machine, the sink in the downstairs loo, and I suspect back into the toilet as well (although I can't be 100% sure on that one).

So I'm guessing theres a big fat blockage somewhere but where's it most likely to be. I'd like to find out the cause before i call out a plumber (if necessary) as I am on a new housing estate and with building still going in very close by. I don't know whether it could be a problem caused by them (or if it's simply dh's over zealous use of loo-roll) but if it is them, they will have to sort it.

Before deciding who is to blame for this blockage, you should try to locate it.

If you check in your back garden you will find a manhole somewhere, open it and see if it is blocked, if it is blocked then you have a blockage somewhere further down the line which will need to be rodded (which you can do easily yourself or blasted with high pressure water)

If the blockage is between your property and the manhole then the blockage had surely come from your property and again will need to be rodded or jetted.

Most blockages are caused by waste building materials, nappys, sanitary towels and animal fats, its a nasty zone down there....!