Master Head Gulping Air

[JLR]

It was a lousy day to go out so it was a good day to work on the boat. I pulled the switch plate off of the box and was able to see behind the head. There is no tubing on the back of the head. Just the intake hose and the discharge hose. I also had some help so I was able to eyeball the pump in the ER as it was flushed and there is no leakage there. But, it is obvious that as the head discharges air is getting in from somewhere because I can hear the bubbles. When the bubbles stop, the head flushes fine. Could just be one of those things, at least for now.

[JLR]

I finally found the answer and wanted to close the loop on this. My experience with GM is that the problem is usually something simple and this fix was no exception. I was getting the boat ready to head South. So, I pulled up my dock hose connected to a bib on my bow and switched over to boat water. Well, don't you know that the head no longer gulps air because the pressure supplied by my fresh water pump is substantially greater than dockside pressure at my home Y.C. Problem solved. Also, since I was using a forward bib for my dockside connection, I used both a pressure reducer and one way valve to make sure I was not pumping water out of the bib into the municipal supply. I guess it was just enough of a restriction to impede the fresh water feed flow rate to the master head. I sure am glad I did not start cutting access panels to try to tackle this "problem."

[SEVEN]

Very happy you found your problem, that was an easy one that we will all learn from.

[JLR]

Problem not solved. So, the search for a solution continues. I will close the loop as soon as I have been informed that the problem has been solved. Darn ... I was hoping that this was fixed.

[JLR]

Works fine when on fresh water pump but not on dockside pressure. Will try to adjust incoming dockside pressure regulator to permit higher pressure and see if that works. If so, quick and easy. If not, perhaps a pump of some sort to boost dockside pressure but not have it connected to my water tank.

[JLR]

Turns out that dockside pressure was up to 70 PSI so I had it lowered to match on board pump. Not sure yet why this would help but perhaps excessive pressure might have created bubbles etc on the intake line? Makes no sense to me and continuing to trouble shoot. If all else fails, I intend to yank out the entire head and put in a Raritan Atlantes based on reviews from the folks here. What are your thoughts on that plan?

[SEVEN]

This is how we all learn. Thanks to all the members who tried to help.

[JLR]

Time to re-group and assess anew. Here is the question. My master head flushes fine when fed by my fresh water pump but not when fed by dockside water. Why? Here is what we know.
First - dockside water regulator shows incoming water pressure of 60 psi, having just been lowered from 70 PSI. So does fresh water pump.
Second - dockside water line and fresh water pump line both go into one feed line in the ER and then to the head.
Third - master head losing flushing prime when on dockside water but not when on boat's fresh water pump.

If this is not solvable, I would consider replacing the head. Aside from legalities, and, assuming only use outside of COLREGS, could the 1.5" discharge line from an Raritan Atlantes be connected to an abandoned salt water through hull of 1" and used as a discharge pathway. Again, all legalities aside--will it work?

[JLR]

Had Raz on the boat yesterday. Confirmed what we knew. When on dockside water, the pressure is too low for the heads. The gauge next to the regulator shows proper pressure. It looks like 60 psi or so. Could there be a check valve of some sort between the gauge and the rest of the inside plumbing? Also, even if there is a regulator connected to each dockside fitting at the deck level, I assume the gauge next the main regulator in the ER is downstream of that deck side regulator. So, the simple question now is how to trace the cause of the low pressure after the gauge which is after the regulator and before the heads and rest of the boat. First thing to do is replace the gauge which if faulty would throw the whole analysis off. Any other ideas?

[bobk]

Check the pressure when the toilet is running. A partial restriction in the line does not affect static pressure, but will reduce dynamic pressure, i.e. when water is flowing. It might be something as simple as crud in the hose bib or a quick disconnect or a washer gone bad.

Bobk