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  #1  
Old 12-15-2008
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Plumbing Question : Head / holdingtank /Overboard

Hello everyone

I am replumbing my 10 years old boat (IP 37) and want to get some advise and ideas.
I removed the old head, the aluminum holding tank and all the hoses yesterday. The new system will have a LaVac head with the MK5 manual pump and a Sealand HTS plastic holding tank. The hose is trident #140 odor shield.
I will install a seperate MK5 manual pump after the holdingtank for discharge to the thru-hull.

I have some questions about routing the waste hoses especially about combining the "direct from the head" and the "from the holding tank" outlets. I will install a diverter valve (Jabsco) after the head to direkt the flow either to the thru-hull or into the holding tank. So far so good. The holding tank has a seperate pickup for the pump-out so that get's connected directly.

My question is about the 2nd pickup from the holidng tank to the thruhull: Of course I will run a siphon break loop after the holding tank. WOuld I need another divider valve to connect the hose to the thru-hull to combine it with the hose coming directly from the head or is it sufficient to have just a Y plumbed?

I hope the description is clear enough. If not I can try to rephrase.



Thanks for all and any inputs.
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Last edited by Volkhard; 12-17-2008 at 02:32 PM. Reason: adding drawing
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Old 12-15-2008
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A better solution would be to route all waste through the holding tank. No diverter is needed, just a T. From the T one line goes to the pump then to the through hull (no vented loop needed-it would just vent the holding tank to interior of boat!) and the other to the deck pumpout. When pumping out offshore you open the through hull. At all other times it is closed which allows the deck pumpout to pull from the tank.An anti
siphon loop is necessary on the inlet to head. The outlet will loop up to the pump and then back down to holding tank. At the top of the inlet loop install one of the two air bleed valves supplied by Lavac. One has a larger hole (the black one). The hole size determines the amount of water left in the bowl after pumping - larger the hole, less water in bowl. The white one is recommended for installation on or above the waterline, the black one for below waterline. The holding tank will vent to outside , probably high on hull side where the last tank vented.
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The above system is the simplest most trouble free way to plumb a holding tank. No diverter valve to stick and less connections to possibly leak. Also with all waste going through the holding tank, there is a lot less chance of it settling out and hardening as does a seldom used tank. I am surprised that IP
used aluminum as corrosion from waste is a problem.
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Old 12-16-2008
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mitiempo:
Thanks for your reply. While I do agree in principal this is not applicable in my case. With the tank being below water level all the contents would needed to be pumped twice (head to tank - tank to thruhull) I personally prefer a direct line head to thruhull for all the times outside the Mile coastal area.

Thanks
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Old 12-16-2008
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Don't you mean - THREE MILE LIMIT???

[quote=Volkhard;417833]mitiempo:
I personally prefer a direct line head to thruhull for all the times outside the Mile coastal area.


The three mile offshore limit applies to the entire coastline - east/west/south etc. Wondering where you come up with the 1 mile?

Last edited by jimq26; 12-16-2008 at 08:33 AM. Reason: better clarity
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I am certainly no expert on this stuff but I have been looking into different plumbing solutions as I recently purchased a boat that will need some new plumbing possibly.

In Don Casey's articles he states that if the head is below waterline then you need a vented loop in at least the discharge from the head to through hull. He states you can do without the vented loop in the intake and he gives reasons for stating that.

I assume there is a way to vent your vented loop that is on the discharge to the outside, maybe combine it with a tee into your tank vent?

Installing a Head by Don Casey

Volkhard, check out the link he shows how to hook up both a direct discharge and both deck and through hull pumpout of the tank.
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Old 12-16-2008
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Volkhard—

While it is true you'd have to pump the waste out of the tank, the real advantage of plumbing the head with no direct discharge is that it simplifies the plumbing and reduces the number of hoses in which waste can sit and permeate the hoses.

Your setup will also require TWO VENTED LOOPS, one for the holding tank discharge line and one for the head discharge line, unless you put the vented loop after the Mk V diaphragm pump, in which case the pump and most of the line up to the vent will have waste sitting for long periods of time and increase the probability of problems with the pump clogging.

If you put the vented loops on each line, then you'll have a lot of hose that has waste sitting in it.
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sailingdog

why is a vented loop required between the holding tank & the through-hull - I've never seen this recommendation before and can't understand why it's necessary if the through-hull is closed when not pumping out as it should be?

Drlove

I think casey is wrong - you ALWAYS want a vented loop in the intake in my opinion
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Some people leave the seacocks on their boats open, regardless of whether they should be or not. If you close the through hull regularly, then the vented loop probably isn't necessary.
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Originally Posted by mitiempo View Post
sailingdog

why is a vented loop required between the holding tank & the through-hull - I've never seen this recommendation before and can't understand why it's necessary if the through-hull is closed when not pumping out as it should be?

Drlove

I think casey is wrong - you ALWAYS want a vented loop in the intake in my opinion
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Old 12-16-2008
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to jimq 26 :

Of course it is the 3 mile limit! I am aware of it and obey it. When I wrote the reply my num/lock on my keyboard must have been off and after spell checking it posted right away. YES within 3 miles AND in any no discharge zone everything needs to go into the tank.

to everybody:

I am planning 2 vented loops for the discharge side and a kind of vented loop (pinhole in a looped supply-line with the fitting that came with the LaVac head). My layout has the MK5 pumps just underneath and before the vented loops to minimize the amount of effluent sitting there. From the loops everything will be plumbed to be downhill going either to the holding tank or to the thruhull. I believe my plumbing scheme is okay so far. The real question was the point were the discharge line from the holding tank meets the direct discharge from the head both (with vented loops above sea-level!) meet just in front of the thruhull: diverter valve or just Y hose connector?
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