Holding Tank Pipe Connections Using Y-Valves

bateau57

bateau57

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Some background. My boat has a Lavac toilet which is very simple and has the usual Henderson MkV pump and works well. I have built the holding tank myself from ply, fiberglass and epoxy and its for under the V-berth. For the record, the tank has 10 coats of West System epoxy inside using 422 barrier additive plus fiberglass mat.

To install the waste system, some yachts I know use 2 Y-valves; 1st Y-valve to to control the pump source from either the toilet or the holding tank; the 2nd Y-valve is used to direct pump output to either the holding tank or overboard. As many will know in the Med finding pump out is difficult so the plan is to pump overboard where it is legal. This installation allows the source to be switched to holding tank and the output to be switched to overboard and covers all 3 use cases 1. Pump toilet waste overboard 2. Pump toilet waste to holding tank 3. Pump holding tank contents overboard

This all seems totally reasonable until you read the Jabsco Y-Valve instruction manual and then inspect the Y-valve. The Y-valve is directional, has a single input and 2 outputs and is really only to control the pump output from the instructions. The Jabsco Y-valve has direction arrows on the body of the unit. The Y-valve for the source would have the output connected to the source for the pump being either the toilet bowl or the holding tank thus the flow would be from the output to the input. The reverse flow to the arrows.

This 2 Y-valve setup seems to offer the simplest control options over the waste. The advantages are; It is simple (1st rule of robustness), one existing pump, no macerator pump or second pump required. The problem is this breaks the Jabsco rules in the instruction manual for installing the Y-valve.

My question then is this. In practice does this installation work Ok? Do you know of blockages or problems when installing the waste system this way? What are the other options?

Thanks
 
In one of the regular 'Lavacs are superior to all other toilets' threads it was pointed out that a common cause of problems with a Lavac is that a plug of tissue can get stuck where a pipe is joined to a spigot and the bore narrows. The fact that you can't 'pump as you go' with the Lavac is the source of the problem and paper economy the solution.

You might consider a simpler option - pump all toilet discharge to the tank. You can then pump out the tank whenever you are in suitable waters. As a bonus you can put a Y valve on the suction side of the 'out' pump so it will also suck from the bilges, thereby giving you an emergency bilge pump. The 'out' pump won't block because the waste will be macerated by the motion of the boat (pun intended).
 
Agree with snowleopard - pump all waste through the holding tank. Also you might be able to have the outlet to the sea from the holding tank gravity fed - just open the valve and associated seacock and the waste will self-discharge. You still have the pumpout outlet but no Y valves needed.

Mark
 
I installed the same system as you are proposing 7 years ago and it's worked perfectly ever since. I did use Henderson diverter valves, though I don't suppose that would make much difference.

I have one diverter immediately behind the bowl and the other in a locker under the adjacent basin. These allow the direct pumping to sea as usual, or direct to the holding tank. We do not have a separate pump-out outlet on deck for shoreside use since we've have yet to come across any such facility in the Med or Caribbean, and don't use marinas here in the UK.

The system is incredibly simple to use and the duel valve set-up allows the holding tank to be thoroughly flushed through when required.

I note the comments above regarding blockages on a Lavac, but have to say that in the 20 odd years we've used ours, it has only blocked once - when a young lady visitor tried to flush a monthly article. Removal literally took just seconds via the screw-off pump front.

PM me if you have any concerns, though I can assure that even with some years of full-time cruising, we've never had a problem.
 
I recently fitted a simpler system to Aeolus, essentially as follows:

Toilet always discharges into the holding tank.
Holding tank discharge point is split by a Y-piece (not a value). One side goes to the deck fitting, the other to the through hull fitting via a manual pump.
For flushing the tank I put a second deck fitting in which leads down to a second Y-piece which joins the toilet discharge into the holding tank.

No values to operate. To empty at sea, open sea-cock and drive manual pump. To empty using a harbour facility keep sea-cock closed and rise out as appropriate from the deck.

Still on season one, but all seems OK so far.

Jeff.
 
This is not the layout suggested by Blakes if you want to use the same pump and keep the independent direct to sea. If you PM me an e mail address I will scan the schematics for you.

BTW pity you did not go for a gravity system - so much easier!
 
I too have recently installed a Lavac with two diverter valves as described by the OP. We have only used it for a couple of short cruises so far but it seems to be working well.

My Lavac has the electric Jabsco pump and I have installed both valves in easy reach from the helm and added a switch to the dashboard so that I can empty the tank under way without leaving the helm.

I originally used diverter valves from Marine Superstore. They were AAA brand and were completely useless. The one on the inlet side sucked air so that the toilet would not flush properly and the one on the outlet side dripped sewage!

I replaced them with valves from Lee Sanitation and have had no leaks since.
 
Good point there. Cheap valves can be bad news. It's worth spending a few quid to get a good one.n <£10 is useless, a good one is going to be >£30.
 
I used two types of Y valve for the system in our Westerly Storm. The arrangement through the Lavac offers the option to pump direct to sea, to holding tank or pump out holding tank. I have a Whale diverter installed through the bulkhead in the heads to select straight to sea or to tank. On the bulkhead in the cockpit locker ( tank is installed below locker boards) I have a Jabsco diverter, which selects the tank pump out option. This was chosen because the ability to vary the outlet angles made it easier to route the pipework. In three years of cruising including a three month trip down to the Med and two years in the Med it worked really well. The only blockage was caused by a wet wipe inadvertently dropped down the loo.
I would recommend a Lavac pump strip down at least once a year to clear scale build up and also to "exercise" the diverters regularly. If left in one position they can sieze up and the (usually) heavyweight action to budge them can derange and damage the internal seals.
I would strongly advise against opting for cheap diverters -- guaranteed grief!
Gravity drain was not an option for me considering the location of the tank.

Happy to discuss if you PM me
 
Fibreglass matt, do you mean CSM? if so this wont work with epoxy resin as the resin doesent desolve the binders in the csm( chopped strand matt).
Eposy should only be used with cloth, ie biaxial or woven roven.
 
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