[Amel] Re: Maramu holding tank

jjjk12s <jjjk12s@...>

I have added a couple of pictures to Popeye's folder including one of our holding tank and a sketch of the setup I have used.

Dave - I expect there will be a logical reason... maybe there is a stand pipe extending inside the tank, or it's designed to be used with a Y valve. The mysteries of sewage...

John, Maramu #91 Popeye

--- In amelyachtowners@..., Dave and Merry wrote:

John, you're correct on a better way to plumb the tank! Unfortunately, that's the way the tank (which came from Amel) is constructed and it was already installed when we bought the boat. So we do pay close attention to the toilet pump and joker valve and luckily have not had a problem. But your post certainly reminds me to keep an eye on it!


On Feb 1, 2013, at 3:33 PM, jjjk12s wrote:

Dave of Air Ops,

You say the pipe goes from the head to the bottom of the holding tank. I wonder why it is set up like this? What stops the tank contents from returning to the toilet if the valve on the toilet is slightly leaking? What happens if you need to service the toilet and the tank is not empty?

If the pipe goes to the top of the tank only the contents of the pipe can return to the toilet if the joker valve is not 100% sealing so an overflow (yuk) possibility is avoided. The toilet is normally flushed so that just clean water is in the pipe.

It is a good idea to move the fascia forward. I also considered this especially because it would allow for a bigger holding tank. If I had not already got a tank that fitted behind the existing fascia I probably would have done this. It would also neaten up that area behind the toilet.



--- In amelyachtowners@..., Dave and Merry wrote:


Late response since we're out and about in the Sea of Cortez, usually without wifi. In response to your questions, unfortunately I don't have a picture of the holding tank. But it fits up against the deck in the aft part of the locker space. It does have a deck pumpout fitting. The shelf floors were cutout to accommodate the tank. One hose runs from the head to the bottom of the tank, then another hose from the tank to the thru-hull. The thru-hull valve seals it off or permits it to be emptied into the sea when appropriate.

Our aft head now is plumbed directly to the thru-hull, via a vented loop. We don't use it in situations that would require a holding tank.

When you remover the fascia, consider reinstalling it inboard so it sits directly above the lip of the floor pan behind the head. We did that, extending the shelves inboard with 1/4" plywood, and gained considerable storage space without impacting the head. It's just a matter of adding some new cleats on the forward and aft bulkheads and then reattaching the fascia to them. On Air Ops, I actually built a new fascia with slider doors.

Good luck,


On Jan 31, 2013, at 10:22 PM, Andy wrote:

Hi John,

We intend to do something similar in one of the heads, we like simplicity.

How difficult was it to remove this fascia ?

Can you give me any pointers ??

Thanks in advance for your feedback.

Kindest regards


--- In amelyachtowners@..., "jjjk12s" wrote:


I put in a holding tank which sounds like the same arrangement as Air Ops but ours is in the aft head.

I removed the fascia covering the storage area and had it resprayed and then reused it, although it would be easy enough to make a new one with the cutouts in different places. I cut segments out of some of the shelves behind the fascia which are thin plywood - not right to the edges where they are laminated or totally removing the shelves, but just enough to make space for the tank. What is left of the shelves is likely just as strong as original and the remnants of the shelves chock the tank in place.

The outlet from the toilet goes up behind the fascia on the left side of the tank to the side at the top of the tank. The outlet from the tank is at the bottom of the tank just above the seacock on the left side. A vent comes out of the top of the tank through a charcoal filter which sits on top of the tank and to a stainless steel vent fitting in the near upright part of the deck molding by the portlight. There are no pump out facilities here so I don't have a pump out but that could also be added.

The only problem is that there is not much room so the tank is not huge. The only valve is the seacock and there are no Y valves. The tank I used was previously mounted on the bulkhead under the sink and was emptied (when the pump worked) by a diaphram pump. As the tank is semi-transparent it is possible to just see the level or easy to see the level by shining a torch but some other means of checking the level could be used. The tank should not be allowed to overfill or the charcoal needs to be replaced. I can't think of a simpler system and nearly all the pipework is behind the fascia which can be removed if necessary to access the tank, vent filter and pipes.

John, Maramu #91 Popeye

--- In amelyachtowners@..., "Andy" wrote:

Hi Dave,

Just going through some old posts.

We're having to install a holding tank on our Maramu. The set up you have in your forward head sounds good. Do you have any photos ??

What system did you end up retro fitting for your aft head.

Any information much appreciated.


--- In amelyachtowners@..., David Wallace wrote:

Hi Ross,
Air Ops (Maramu #104) has a holding tank foward which was installed in the boat when we bought her in 2000. It was supplied by Amel and is mounted behind the head storage panel, in the aft upper half. The head pumps up into the tank and then gravity feeds overboard if the single valve at the thru-hull is open. There is a vent/pump out fitting on the deck next to the toe rail. We've had no issues with it.
There was no holding tank in the aft head so we installed a LectraSan which fits nicely but we've never been happy with it and wouldn't get one again. The boat is now in Mexico and we primarily use the forward head but will have to figure out a solution before we return her to the US. The holding tank from Amel would work just as well in the aft head but it's unlikely they still have them. Might be worth asking, though...

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