The Troughs of Despair

My “job” at the allotments is to keep the water trough lids in working order.

But we also have to train allotmenteers to use them properly. The signs telling them not to wash hands/tools/ veg in the troughs seems to working reasonably well.
Now we are launching a campaign to get them to close the lids when not in use. This is due to green algae, bird droppings, insects laying eggs and evaporation.

The committee member I discussed it with (MrsWW) said bought signs were too expensive - make a stencil

So far I have learned that the letter P is a problem