On board water pressure

[jjrowan]

Tried flushing the anti-freeze from the on board water tank, sinks, shower, toilet and grey water tanks (no place to dump black water just yet). The drain on the water tank has a brass spicket but when I opened the handle on it, it wouldn't drain, nothing came out. I blew compressed air into it and it cleared whatever was blocking it and I drained that tank. I connected a hose to the city water feed, flushed the sinks and showers of anti-freeze then drained the grey water tank. I filled it the on board tank and tried using the pump to test the system. The pump came on but water only trickled out of the faucets. I found the valve coming out of the on board tank had an inline filter which appeared to be completely blocked. I cleaned it, reassembled the system hoping I'd have pressure but still a trickle. Watched water tube coming from tank, goes to a T valve, right side goes to drain, left side goes to pump. It appeared the connection to the pump is sucking air in somehow. I tightened the hose clamp but sill pulling air somehow. Think I have to replace hose or valve or both. Don't understand how with all the water in tank and gravity it isn't forcing water into the pump. As I write this I realize there's a square device that might be another filter but I can see into it and it doesn't appear to be blocked. I plan on taking a clear tube from water tank to the pump bypassing T valve and secondary filter to see if it solves the trickle problem.

Any other suggestions?