Water system woes

[lakeguy72]

For 31 years my F-32 water system has worked fine. You fill the tank, turn on the pump and water comes out each faucet. That's the
way the season stated-then no water out of any faucet. Same result using dockside water. The flow thru the filter is fine with the output hose disconnected. Today, using a water hose hooked up to the shower(cold side) I got all faucets to flow like normal. I should have gotten flow out of the "free" end of the hose that was disconnected to the filter--nothing. It appears that there is blockage in the cold supply line prior to the tee going to the hot water heater(as the water is going thru the heater and out the HW faucets when pressurized from the shower end). Could there be a check valve in the cold supply? As you may know the cold supply line runs down the port side tucked under the gunwhale and difficult to see/access with saddle tank in the way. The HW feed, cold feeds for the galley, head and shower are teed off the main line.
My next step is to cut an access hole in the salon floor as far outboard as possible to see what's there. Has anyone had this problem?
Thanks

[srokag44]

The dockside water connection does have a check valve in it. This prevents water from spraying out when you are operating from the tank and fresh water pump. Sometimes these check valves can get stuck shut. I was able to open mine by shoving a rod into it and forcing it open.

[lakeguy72]

Hi, thanks for your reply. The blockage is beyond the dockside connection and my "whole house filter". I get normal flow up to the point just before the tee to the water heater. When I reversed flushed the system using the shower faucet the water went thru the heater as well as all the other faucets. I did this with the line from the filter disconnected and no water dribble or otherwise came aft of the heater line. This is telling me there must be a blockage just before the tee. I took the heater out of the loop by using my winterizing by-pass connection. I'm going to run a line from the filter to the heater feed as by-pass the problem area to see what happens.