SV Pilgrim - 1979 Morgan 382 - Homeport: Beaufort, NC

Sunday, August 3, 2014

Head Plumbing Diagram - Follow Up Post

Note:  To preserve the narrative of Pilgrim's refit this post and diagrams will remain available to readers.  There are design flaws in the plumbing diagrams depicted on this post.  If you are seeking black water diagrams for use on another vessel, then please see our September 30, 2014 post - Holding Tank and Blackwater Plumbing Complete.  Thanks.

Thanks for all the follow up comments and questions about my proposed head plumbing for Pilgrim.  I am not a marine plumbing expert.  Additional perspectives provide me with the opportunity to assess my proposed system prior to committing time and resources to the installation.

A couple details to note in the original diagram (above)...
To comply the laws that require the valve permitting waste to be discharged from the vessel directly into the water, I will need to place a lock on either the thru-hull fitting or on the two "Y" valves closest to the holding tank.  My preference would be a single lock on the thru-hull.

The valves depicted in the diagram are Forespar "Y" valves. We are re-using valves removed from C'est la Vie.

To clarify my intentions I created a few new diagrams that illustrate the flow of waste through the system in various situations.

When set up to flush the head directly overboard the waste will follow the path highlighted in red below...

When set up to flush into the holding tank waste will follow the path highlighted in red below...
When set up to empty the holding tank via a pump out facility the waste will follow the path highlighted in red below...
When emptying the holding tank offshore via the macerator pump the waste will follow the path highlighted in red below...

I hope the additional diagrams assist in illustrating my intentions.  Please keep posting questions and comments.


  1. Jeff, Your diagram looks good to me but the Y valve between the head and the holding tank or the next Y valve may be redundant.

  2. Bud,

    Thanks for looking over the diagram. You are not alone in suggesting that the "Y" valve just downstream of the holding tank used to select macerator or deck pump out could be replaced with a simple "T" junction.

  3. I have a system where waste is always pumped to holding tank. And from tank either to deck or to thru-hull. It is very simple and reliable and you do without any Y-valves.

  4. I have the same system as Sami. Works great. Don Casey has it diagrammed in a West Advisor article at Basically your holding tank becomes a manifold for all waste disposal options.

    It also has the additional advantage of when a 19-year-old Coastie asks to see your Y valve, and you explain that there is none, he checks off the compliance box very quickly. To be totally compliant in the US, you can lock off the overboard discharge seacock, or in Canada/Great Lakes cap it.


  5. Sami & PK, I did consider the option you are both describing. If our primary cruising area were US & Canada coastal & inland waters I believe it to be a good option as pump out facilities are typically available. Pump out facilities are few and far between in the Bahamas, Caribbean, and Central America. This would place the entire head system at the mercy of the macerator. If the macerator failed and pump out facilities are non-existant then the head is rendered useless until the macerator is repaired or replaced.

    I would actually prefer a manual pump vs. an electric macerator for the holding tank discharge, but due to space/access constraints installing a manual pump would increase the complexity of the system.

    Thanks for sharing your thoughts.