4207 Overboard Vent Clogged

[Morningstar4207]

Hi, I'm having some issues with my fresh water system. I noticed that my overboard vent on the transom is not releasing overflow water when I overfill my fresh water tank. Does anyone know how to troubleshoot this or replace it? We have a 1986 4207 with a metal fresh water tank located under the bed in the aft cabin. Thank you!

[bud37]

It may not....it is an air vent and may present enough height restriction so when the tank is full it just backs up the fill pipe. These vents if installed properly should have a loop which will increase further the effective height of the vent depending on how much loop there is.....could even be kinked.

....good luck with your project.

[Cooler]

Are you having any issues with water flow? If not, then it may be normal to not see overflow at the vent. The loop in the line is designed so water does not go out, or in. er

[Morningstar4207]

I am having problems with flow. I am not able to access all the water in my tank. I fill it and then the flow stops after I wash dishes twice and I have to fill it again to get the water to flow again. Before this issue with flow I was able to wash dishes, fill drinking water reserves, shower etc for four days before filling the tank. I think my lines are clogged and/or there is significant air in the lines.

[km1125]

If the vent was causing that issue, then removing the fill cap would be a good test. The vent is just providing a path to fill the tank with air as the water gets drawn from it. If you remove the cap and still have a problem drawing water, then your problem is solely within the water piping from the tank, to the pump, to the faucets.

If removing the cap DOES resolve the issue, then you can focus on the vent line and figure out where it's restricted.

[Viper]

As km mentioned, remove the deck fill cap, if the problem persists, it's not a venting issue. Before this problem started, would an overflow come out of the vent and now it suddenly doesn't? If accessible, you can check the vent line by removing it at the top of the tank and see if you can blow through it. Also check the hull vent to see if it's blocked with anything like webs, mud (wasps), etc.

If you determine it's not a venting issue, see if you have a strainer on the suction side of the pump between the pump and the tank and ensure it's clean and not clogged. Does this happen if you only use cold water? If it works fine with cold water only, to see if there is a check valve on the hot water heater. If there is a lot of air in the system, then you have a leak somewhere or your hot water tank isn't quite full and needs to be purged.

This may also be a failing pump. It could have a bad check valve and instead of pressurizing the system, it's backflowing to the tank until you add more water in the tank and overcome the pressure leaking through the valve. Don't know how big or tall your tank is but it's a possibility. Turn the pump on and let it pressurize the system. When the pump stops, shut it off at the breaker panel and don't use any water. After a few of hours, turn the breaker back on and listen for the pump. If the pump cycles, you have a leak somewhere in the system, or it's bleeding back through the pump.

[bud37]

Interesting you have a metal water tank... but the screen filter ( if you have one ) before the water pump ( suction side ) may be worth checking out...