Foretravel Owners' Forum For owners and Fans of Foretravel Motorcoaches September 16, 2025 ...

Fresh water tank problem with small vent hose

July 19, 2012, 02:38:51 am

I read about potential problems by replacing our large diameter fresh water tank vent hose with a smaller diameter hose when rerouting to eliminate bulkhead wetting.

I remember reading that some are considering running a water hose size through the bottom of the bay floor.  This is probably a bad idea because when filling the tank with city water, air in tank will be pumped out the vent and a small long hose may cause the plastic tank to pressurize if water comes in faster than the tank can vent.  And if the hose crimps anywhere, there will for sure be trouble.  Tank also has to allow air back into tank as water is pumped from tank.

Quote Selected

Re: Fresh water tank problem with small vent hose

Reply #1 – July 19, 2012, 07:37:58 am

Hey Guys,

I couldn't agree with you more as to why a small vent hose is a bad idea. When I rerouted mine I stayed with the same size and made it long enough to form a P trap. Presumably the water trap will keep critters from traveling into the tank.

Quote Selected

Re: Fresh water tank problem with small vent hose

Reply #2 – July 19, 2012, 11:15:01 am

I used the same (or nearly the same) diameter hose too.  I put screen over the end to present critters from getting into the tank. 

Quote Selected

Re: Fresh water tank problem with small vent hose

Reply #3 – July 19, 2012, 06:54:30 pm

I don't understand the P trap on the vent hose. Will water in P trap hinder or increase effort air from being 'sucked' back into hose when water pump is running? And the same for exhausting air from tank when filling tank from city water? The vent hose does more than direct overflow water from the tank.

Quote Selected

Re: Fresh water tank problem with small vent hose

Reply #4 – July 19, 2012, 07:11:06 pm

The P trap does offer slight resistance to air flow in/out of the tank. It actually operates as a scrubber when air is drawn in, trapping any dust/dirt in the trap and flushes it out the next time the tank is filled to capacity.

Quote Selected

Re: Fresh water tank problem with small vent hose

Reply #5 – July 19, 2012, 09:04:20 pm

I have always wondered about the glug, glug sound as air is either drawn in or forced out of the tank. Do others notice this? I am guessing that's just how it is.

Quote Selected

Re: Fresh water tank problem with small vent hose

Reply #6 – July 19, 2012, 09:12:50 pm

Dick, When I hear the GLUG GLUG  It is time to shut off the water.
Gary B

Quote Selected

Re: Fresh water tank problem with small vent hose

Reply #7 – July 20, 2012, 07:50:58 am

Remember the P trap in the winter. Gam

Quote Selected

Re: Fresh water tank problem with small vent hose

Reply #8 – July 20, 2012, 08:40:33 am

Not a problem with a heated basement.

Quote Selected

Re: Fresh water tank problem with small vent hose

Reply #9 – July 20, 2012, 09:03:10 am

                       I re-routed my fresh water overfow yesterday. I considered a P-trap but where we live in Maine it would be one more thing to winterize. Went with the screen like other's have done.

                    Dean

Quote Selected

Re: Fresh water tank problem with small vent hose

Reply #10 – July 20, 2012, 12:39:01 pm

Unless one overflows often, that puppy will dry out.

Quote Selected

Re: Fresh water tank problem with small vent hose

Reply #11 – July 20, 2012, 12:59:55 pm

It never dries out as we fill the tank until it overflows, to ensure it is full. As a fulltimer this is done on a regular basis.

Quote Selected

Re: Fresh water tank problem with small vent hose

Reply #12 – July 20, 2012, 02:16:48 pm

I installed a float switch near the full mark. We fill through an RO filter system using a 24VAC auxiliary pump. We fill often, but the tank does not overflow. When parked in an appropriate location, we leave the water hooked up and allow the float switch to control the pump and valve. The tank is full when we are ready to travel.

Quote Selected