manual pump

Hi, I can pump in fresh water into the bowl but then I cannot send it to the tank after I switch to dry operation. First there was a back-pressure but I could pump. I emptied the tank. So now there is no longer a back pressure. However, I cannot displace the waste into the holding tank anymore...

Our boat came without the actual foot pump and faucet assembly. It was there at one time, but was removed. The rest of the parts (seacock, hose and a hole in the counter top) are already there. So I got tired of looking at the hole at the bottom of the cabinet, always opening a wrong seacock...