Started the Herms build today.

First use in anger failed! Although I drained and recycled a jugfull before starting the HERMS, the small filter clogged quite quickly. Having cleared it out I could then not restart it due to not having a bleed point installed to remove the air from the closed system to allow the wort to reach the pump. Finished the mash normally and then once the boil was on, I refilled the mash tun with all grain still present and experimented with the rig for a while.
Required modifications have been noted and will be made before the next brew.
Incidentally, it did work of sorts for a while during the mash and the result was a higher SG than expected. Should have been 1048 and came out at 1049. Sorry no pictures as I became engrossed with trial and modifications.
Graham

My filter would always block until i started waiting a good 10 mins before turning the pump on and by reducing the flow too .

I don't know if I've missed something here - but why bother with a filter? The mash bed is the filter. I use a £15 solar type pump and its never clogged at all.

As above, I leave the mash for 5-10 minutes after doughing in and then start the pump slowly. First runnings through the pump are a little rough and cloudy, a few small bits of husk go through, but they're filtered by the manifold, so they can't be big enough to damage the pump and all pass through, back to the top of the mash. By 30 minutes, the finer particles are all but gone, and and after 60-90minutes its crystal clear.

Is the filter an unnecessary feature, or does it serve another function?

R

a grain bag is a simple large particulate filter that wont clog and it makes removing the spent grain from the tun a doddle too..

I personally use a plastic plate floating on the top, dropping a silicon hose. No splashing or grain bed disturbance and i fly sparge, so it works fine for me, but i agree, a simple return manifold is easier in a way. I once made an inverted t shaped return manifold, which had elbows which pointed up, to make fly sparging into the head of water over the grain bed easier... If you can imagine that...