500' is quite a depth. I was designing a similiar unit for 300' but I soo demolished the idea when I starting realizing the pressures. Being a scuba diver you learn that 1 bar metric = 14.7 PSI US and this is at sealevel. increasing 14.7 (or 1 bar) every 33' With the phsyics out o the way here is what you are looking at Sealevel 14.7 33' 29.4 etc etc to a point of where 495' is 235.2 psi That is a lot of pressure on plastic not to mention the seals and glass mounting for the cover. If you look at the pressure rating on the PVC I don't think it will handle this, depending on whether you use schedule 40 or 80 vs the pvc diameter. Eddie, kc4awz -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics