I've read the previous forum correspondence on holding tanks with great interest, as we'd like to install one in Delphine. We like the simplicity of the tank mounted in the wet locker with gravity feed to the sea (as in Sunflower) - but we've decided that the wet locker is too valuable a hanging space for wet oilies to lose. I've therefore devised a layout in which the tank will go into the forepeak, in the forward triangle beneath the berth, and I attach a sketch showing the layout. It has the advantage that we can choose to discharge directly to the sea or to the holding tank, so that we don't have to pump the holding tank after every use of the heads, and the choice of direction (ie, to sea or to holding tank) will made by valves in the heads. Our seacocks are located beneath the forward berth, with access through a small hatch, and we plan to put the manual pump to empty the holding tank nearby, or in the heads. A disadvantage to the arrangement is that there are quite long pipe runs between the heads and holding tank, so that, when we use the holding tank, quite a lot of water will have to be pumped to make sure that the contents of the heads reach the tank. The normal discharge pipe from a holding tank seems usually to be plumbed in from the top of the tank, but I think it would be less likely to block if it went from the bottom of the tank. On the other hand, it seems a good idea not to have any openings in the bottom of the tank, just in case the connection leaks! Does anyone have any views - or experience?

Many thanks

Gilliane

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My boat had a holding tank in the forepeak, but when I got her it was disconnected. I think the heads had been replaced to put a Jabsco in place of the original RM69. I've been trying to work out how to re-install the tank, along the lines you are thinking of, but with a pump out connection too - so far I haven't arrived at a good arrangement, so I'll be really interested in how you get on.

The tank I have is like the 60l Plastimo one. I had read some things that suggested that the Whale 2 way valve was better in service than the vane type of selector valve [Forespar or TrueDesign], but I have no other information on that.

Good luck!

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This is an interim report as our holding tank is now installed, but Delphine isn't launched yet, so we haven't yet been able to try it out.

We used the layout of my earlier forum posting, with a standard Vetus 40l tank installed in the forepeak. The two seacocks (inlet water and outlet waste) are both installed at the aft end of the forward berth. The inlet water goes straight to the toilet, and the outlet then went through a loop in the wet locker (rather annoyingly looped over the hooks, making it difficult to use them) and then to the outlet. In the new arrangement, the water inlet runs in exactly the same way and the outlet runs aft to the unused space behind the basin in the heads.

The first diverter valve is in the cupboard below the shelf under the basin and determines whether the waste goes straight to sea or forward to the holding tank. If it goes to sea, it does so through the loop as before, but this is now fitted with an anti-siphon valve. The loop itself is at the aft end of the hanging locker, space which was previously inaccessible and not really useful, and the hanging locker hooks are now more accessible. To empty the holding tank, the second diverter valve, which is just above the shelf in the under-basin cupboard, is set to connect the holding tank to the loop and hence to the outlet. The vent from the tank runs aft to the aft end of the wet locker, and exits in a new fitting just above the shower pump-out. The waste is pumped from the tank by a pump mounted in the heads, just below the toilet roll holder. A marina pump-out connection is fitted from the tank up to the anchor locker, running in a space forward of the forward berth and therefore concealed. A gauge (electric) showing the level in the tank is mounted in the heads.

The restricted space has meant that this has been a really difficult system to fit, and we're very lucky that the guy who helped us with maintenance on Miss Fidget is also available to work on Delphine. He's determined and resourceful - and said he enjoyed the challenge!

There are both good and bad aspects of the final arrangement. The holding tank has a reasonable capacity, given that we have the choice for each use of the heads whether or not we use the tank. The valve showing its state is very accessible in the heads. The seacocks have to be opened from outside the heads, as before, and all the other controls are in the heads. The two diverter valves are completely hidden so the only visible addition is the pump to empty the tank, mounted below the toilet roll. We've gained usability of the wet locker since the loop is no longer in the way of wet waterproofs.

On the down side, all the pipe runs are quite long. This won't be a problem for direct discharge - we'll just pump a few more times - but it does mean that each use of the holding tank will require sufficient water to be pumped through to clear the pipes, and this will use up the capacity of the tank. We've lost space in the wet locker as well as gaining, since the lower part of the locker is filled with extra pipes running to the diverter valves, so long waterproofs will have to be folded.

I'll report finally when we've used the system in earnest for a while...

Gilliane

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Gilliane,

How's the system working? Any chance of some pictures of where you installed the diverter valves?

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Hi Dick

I can report that the holding tank arrangement has worked very well. We haven't used it very much - just a couple of occasions overnight in Newtown River. The diverter valve giving the choice of direct pump-out or pump-out to holding tank is a bit awkward to reach in the cupboard under the handbasin in the heads, but is very easy to use. As we foresaw, we could be limited by the size of the holding tank (there was only room for a 40l tank) and the length of pipe runs, and the gauge showed the tank to be getting on for a quarter full after only two uses. If we were planning to use it for a long period of time, we'd probably have to reduce the number of pump strokes for each use. You say that you already have a 60l tank on Dark Star, so you'd have significantly more capacity than we have.

We've also found the tank very easy to discharge and flush through. We've done this while hove-to, so that the boat has been reasonably level and stable, and we could use the gauge to tell when the tank was close to empty.

I'll try to take some photos next time we're on the boat.

Best wishes

Gilliane

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Hi Dick

I now have some photos, as requested.

The first of the photos shows the diverter valve, valve 1, in the lower part of the cupboard beneath the basin in the heads. The inlet pipe comes from the heads, controlled by the pump on the RM69 toilet, and the valve can be set to discharge either to valve 2, in the upper part of the cupboard and thence directly to the sea, or to the holding tank. In the photo, the valve is set to discharge to valve 2, as shown by the arrows. To discharge to the holding tank, the lever would be rotated clockwise.

The second photo shows the diverter valve, valve 2, in the upper part of the cupboard. The outlet from this valve is via the anti-siphon loop to the outlet seacock and the sea. The inlet can be switched between the pipe from valve 1 and the pipe from the holding tank. In the photo, the valve is set to discharge from valve 1 and would be rotated anti-clockwise to discharge from the holding tank. The red and blue pipes in this and the previous photo are the hot and cold water supplies to the taps in the basin.

The third photo shows the front face of the pump used for emptying the holding tank. This is a manual operation similar to a bilge pump. The pump itself is mounted inside the wet locker, in-line in the pipework between the holding tank and valve 2.

There are now a lot of pipes running at a low level inside the wet locker. These are the discharge pipe from the toilet to valve 1, the pipe from valve 1 to the holding tank, the pipe from the holding tank to valve 2, the pipe from valve 2 via the anti-siphon loop to the seacock beneath the forepeak and the vent pipe from the holding tank to a new vent in the topsides above the drain from the basin. The anti-siphon loop is now at the aft end of the wet locker instead of the forward end, and this has released useful hanging space at the forward end.

Good luck if you decide to go ahead with your holding tank on Dark Star...

Best wishes

Gilliane

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