how to make head flush pump more efficient

[fulvio]

In the process of installing a new hose under the head sink to feed the galley salt-water spigot I learned that having the head intake hose on a through-hull different from the one for the head sump pump dramatically improved the head pump efficiency.  Here is how my three through-hulls under the head sink were plumbed originally:

1. engine raw water intake
2. head intake, teed with sump pump discharge
3. head sink discharge

Wanting to add my galley salt water intake to the combo, I reasoned that it seemed to make more sense to have two intakes teed together and two discharges teed on their own through-hull, instead of mixing intake and discharge on the same through-hull. 

When I did, the head pump flow was much faster and easier than before.  The reason for this, as I discovered, is that when you activate the head pump in the original configuration, you are also sucking air through the anti-syphon valve on the sump pump drain line, making the flush a lot more inefficient.

Unfortunately, there is a reason why putting the sump pump discharge on a T with the head sink discharge is a bad idea:  when you start the sump pump, it will push foul smelling water that stagnates in the hose up the sink.  Yuck!

A possible solution might be to add a shut-off valve in the sump drain hose between the through-hull and the anti-syphon valve, with the disadvantage that one has to remember to open it before starting the sump pump.

Does anyone have a better idea?

I do like the head pump to run that much more smoothly.

[cmainprize]

A couple of options jump out to me.

1. add another thru hull
2. put a check valve on the sink drain
3.put a y valve on the sink drain sump pump line and choose which one you are going to use.  This is how the mk 11 are set up from the factory with the ice box drain and shower sump because they are connected to the same thru hull drain.  without this valve the pump would shoot the shower water into the fridge.

[Ron Hill]

Fulvio : If you don't want to add another thru hull, then go with Cory's #3 - the "Y valve". 

If you go with another thru hull for your saltwater pump add the thru hull where the factory did - just on the bow side of the electric fresh water pump under the galley.  - see page 4.3.1 of your Catalina owners manual !!!

A thought

[Stu Jackson]

We T-eed the head inlet to the sink drain.  Whole different reason discussed in most of the head odor threads.  This left the sump pump separate.

[Ron Hill]

I'm back on the boat and did some measuring.  That double on the middle thru hull installed by the factory is under the water line by at least 3 inches.

Why the anti syphon of the shower sump could affect the head pump is mind boggling.  I haven't had a problem in the past 26 years with pumping water into the head.  We lived on the boat for 8/9 months and average over 110 overnights in the other 25 years!!

I suspect that the head pumping (lack of water) is because the "O" ring on the base of the pump is worn!!

My thoughts

[fulvio]

Ron,

I'm not saying the factory install is a problem.  Otherwise, continuously living aboard full-time for over 13 years would have been quite a different experience.

I am merely suggesting that empirically, configuration B works a lot better, for some (albeit subjective) measure of "better".

Configuration A:  "double on the middle through-hull", with head intake and shower sump pump drain T-eed together (this is the factory install)
Configuration B:  head intake on middle through-hull, and shower sump pump drain moved to port side through-hull

I went from configuration A to conf. B, and the head pumped much, much better.  Then I went back to A, and it felt downright sluggish.  (Although, it does work).

I think it does make sense even theoretically:  the anti-syphon valve is just doing its job, which is to break the column of water by letting in some air when there is suction on the downward arm of the syphon.  In fact, when I went back from conf. B to A I could distinctly hear a little sucking sound coming from the anti-syphon every time I pumped the head, which I never noticed before.

Just my thoughts.