[Lab] Grey water tank design

[janick at bergeron.com]

Not really art-related, but given the creativity of the audience, I
thought I'd ask here first. 

I'm moving to the West Coast soon and the house has a large grey water
tank in the crawl space to buffer the rain water collected by the
eavestroughing before slowly draining through a 1" conduit at the
bottom. Given the increasing drought conditions, I want to turn it into
a grey water storage tank by redirecting the existing drain at the
bottom to a tap, and moving the drain to the top of the tank to prevent
overflow. 

Here's what I need: 

- Because of lack of maintenance from the previous owner, there's a lot
of gunk in the tank that can obstruct the drain. I have temporarily
added a screen to the existing drain. Is there a design (maybe an
inverted "L"?) I can use for the drain INSIDE the tank to prevent
floating debris from being sucked in and avoid a screen that will clog
over time and reduce pressure? 

- The tank is not readily accessible so I need a remote water level
alarm/measurement system. Given a 2ft water column creates about 1psi of
pressure, I don't think a pressure sensor will be accurate enough. That
leaves a float-based mechanism. Any idea/suggestions? 
 
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