You know the little ones on the wall, flow just dropped off to a trickle.

The little filter I clean, it is ok, when I take out the filter and turn on the water it blast hard, when I take off the exit hose it is a trickle, indicating there is a blockage inside the unit somewhere.

Any tricks to clean it out.

It is in a rental this one and the land lord wont replace anything of course, gezzzz, he wont even kill the termites eating his house !!!!

Can I just do the flow in reverse and try to wash out what ever is blocking it. I am worried of maybe a pressure switch or what ever in the unit I will break.

Unit is believed to be 8 yo

Any thoughts?

Probably a build up of scale,pretty much what occurs inside a kettle especially in areas with hard water.

Thanks Stoneboy, any suggestions how to dissolve it with it on the wall, well give it a go any way?

I use vinegar on my chrome taps and this works OK. But this is external. Not sure how to get it inside your heater and let it do it's work.

Have to remove it from the wall, turn it upside down and fill it up. Probably take a few hours.

Vinegar would be a start or if you can find a Calcium or lime remover in HomePro or local store. In the states we use a product called Bartenders Friend or CLR (calcium/lime/rust).