Fitting a waste water holding tank

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This topic contains 14 replies, has 8 voices, and was last updated by  racepassage 3 days, 2 hours ago.

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September 5, 2013 at 07:36 #6691
Voltair
Voltair
Participant

We are thinking of taking Voltair around the Balearics in 2014, and would like to fit a holding tank for the heads discharge, which we can either vent to sea when far enough from land, or have pumped out when in harbour.

Does anyone have a boat with a holding tank already fitted? Has anyone experience in designing and fitting one?

September 6, 2013 at 08:38 #14101
Jeff
Jeff
Participant

I’m still thinking of installing one but my local Swindlery quotation of £2000 for the custom-built F/G tank (to fit under the St’bd V-berth) etc, put me right off. That seems to be what other people have been charged/quoted too. I’d like to see more posts on this topic too, as it won’t be too long before we’re being FORCED to have one fitted.
Sea Eagle had a flexible rubber-bladder holding tank under the St’bd V-berth, but I threw it out as it still smelled no matter how much I scrubbed it.
Custom-built Polyethylene tanks seem to be a ridiculous price, getting up towards the £350-£400 mark last time I checked, but cheaper than the F/G option of course.
Jeff

September 6, 2013 at 08:46 #14111
Voltair
Voltair
Participant

We were thinking of using the space behind the cubby-holes in the heads to fit a small one…. but above sea-level, so it could self-drain to sea when you open the sea-cock.

The problem is, Voltair is in Faro, I am in UK so I can’t measure the space until we next go out there…… unless someone already tried this and knows how big the space is…

September 6, 2013 at 08:51 #14121
michael bennett
michael bennett
Participant

Yes I have fitted one, not to difficult to make and fit, it is under the stb.forecabin bunk, and all the fittings, including the changeover valve behind the heads-removeable unit about the sink.
I have photographs etc if anyone interested.

September 7, 2013 at 01:30 #14141

Orion
Participant

In a previous posting I detailed the $75 solution..bought a used 25 gallon abs cube tank, dropped into the space under the stbd settee, just on the other side of the bulkhead, from the head. We use the one existing through-hull for direct discharge, as well as discharge returned from the tank, by a mascerator pump. A manifold, with three large ball valves varies the flow direction/choice. I’ve added another hose, up to a deck fitting, for pump-out. We get boarded and dye-tested routinely, in Southern CA.

September 8, 2013 at 09:15 #14151
michael bennett
michael bennett
Participant

The tank I made and fitted also has a pump-out facility on top, but not through the deck, as I didn’t want to disturb the teak, the same deck fitting is in the tank top, access through the hatch just above it, once the bunk top removed.
I fitted a 3 way valve to divert from the head bowl to the tank, which also has a large ball valve in the discharge pipe to isolate it further. I understand US coastguard will test regularly and also fit seals which can only be removed when away from restricted areas, if found removed or tampered with penalties apply!
I also used my existing Blake outlet with a Y valve, those Blake’s are still the best,the only thru-hull was for the vent, in a reduced size pipe (1 inch) with a nice SS external fitting.

September 12, 2013 at 03:27 #14171
Moderator
Moderator
Keymaster

There is another forum topic where this is discussed, you can find it here.

As discussed on our blog here, we put our 13 gallon holding tank in the space behind the head basin where the cubby holes were. PlasticMart sells a tank that is 25″ x 16″ 8.5″, which we were able to fit by making the following modifications:
1) grinding back the chainplate knee ever so slightly (to fit the 8.5″ dimension) (we pulled and inspected the chainplate first, as access is now more difficult)
2) cutting down the bulkhead under the sink and fitting a shelf over it to support the tank,
3) i believe we even cut the fiberglass liner down behind the sink to also make the opening bigger than the cubby hole cutout.
4) We made a new cover to go over all of it, sized about 18.5″ on fwd end and 16″ on aft end, 30″ in length. This requires a cutout to set the sink in place. We actually made this board in two pieces with a horizontal junction, so we could seal the sink in place against the bottom board, yet remove the top board to gain access to plumbing bits for maintenance (such as the lavac inlet hose vent cleaning).

It’s a nice design because it can be gravity dumped (note, we added a ball valve under the tank that determines whether the tank is open or closed to protect the blakes seacock from the sewage when its being held. sewage is very hard on bronze seacocks. If you do this, be careful about closing both valves as stuff may grow in the enclosed space and create pressure that stops you from being able to easily open the valves).

We also installed a deck-fill so it can be vacuumed out in areas where dumping is not appropriate or illegal. There are more details on our blog page, or I can answer more questions here.

The down side is the small size. It would be nice to have more capacity because we have filled it if we spend several days at the same anchorage (e.g. when we are hiding from a passing storm).

marilyn

September 12, 2013 at 14:50 #14181
michael bennett
michael bennett
Participant

I have looked at your installation which looks very neat and nicely finished, but as you say yourself is rather small for a prolonged stay in a restricted area.
I considered using the same space, but rejected it in favour of a larger one about 50+ ltrs. with no loss of the very useful ‘pigeon holes’ and tailor made to fit in the space under the stbd. bunk.
The space behind and under the pigeon hole box is ideal for fitting the 3 way changeover valve, easily assessable from the cupboard next to the toilet bowl when changeover required.
I utilised the existing manual pump (Henderson Mk11, original I think and working perfectly) to empty the tank, never used it previously as the bowl has its own Jabsco to pump out. Both feed through the Blakes via a ‘Y’ connector on top.

Mike

October 4, 2013 at 07:46 #14391
Gerhard M
Gerhard M
Participant

Hello Mike
you mentioned earlier that you will supply pictures of your installation. I would be intressted in such. can you send me to my email adress?
Thanks
gerhard
Ayla

October 5, 2013 at 18:44 #14411
michael bennett
michael bennett
Participant

Hello Gerhard,

I will forward photos to you by email.

Regards

Mike

October 9, 2013 at 16:05 #14451
Jeff
Jeff
Participant

Hi Mike,
Can you send me the same photo’s please.? I’m particularly interested in the customised tank under the V-berth. I’d like the same arrangement.
Who made up the tank for you & what was the cost.?
One other thing Mike, there were some previous posts on window replacement & Interscrews etc.
Have you, or anyone in UK, managed to find an EXACT like-for-like replacement Interscrew. (The screws are 16mm long, but a 10mm Interscrew nut doesn’t come close to catching it so I’m assuming the original Interscrew nut must have been about 15mm, which isn’t manufactured now).
I’ve been phoning all over UK & it seems be just a choice between too small, or too big.(In which case I have to drill out every hole on the inner frames to take a 6.5mm Interscrew.
Many Thanks,
Jeff

October 10, 2013 at 17:24 #14461
michael bennett
michael bennett
Participant

Hi Jeff.

Everything sent to you.

Also info re widows…. ooops i mean windows, sorry to disappoint..

Mike

December 2, 2013 at 13:12 #14571
Voltair
Voltair
Participant

On Voltair we have now installed a purpose built stainless tank where the cubby-holes were in the heads, that discharges under gravity through the existing heads through-hull. We managed to get approx 48 litres capacity, without any new pumps and only one valve to switch. Because the vacuum heads system pumps such a lot of seawater along with the detritus, we figure that most of the tank will be full of water (once it’s settled a bit). So we have arranged for an upstand pipe inside the tank to about 3/4 height, so that any surface liquid can flow down there and away to sea without discharging anything embarrassing. The switching valve changes betweeen discharging this “water” and fully discharging the tank. The skin-fitting valve means we can contain the whole lot if constrained to do so (though actually it leaks quite badly). The vent pipe is connected to the wash-basin waste, which is on the waterline, so it won’t vent well on port tack (but who cares). I’ve put a loop trap in the basin waste so the vent pipe doesn’t cause smells to come in. The vent pipe is also sealable, so that we can forcibly pump the waste through the tank if gravity doesn’t do the job for us. Total cost was around £800 including 2 round trip airfares to Portugal to transport and install the tank and associated plumbing. I have the tank profile design to hand if anyone wants to try something similar.

September 6, 2017 at 21:33 #26159
John Tyler
John Tyler
Participant

Got a steel one fitted under the stbd forepeak bunk, with a macerator in the tank and a switch in the head, showing level & pumpout option. Amazing that the EU still does not insist on them being fitted.

September 16, 2017 at 23:49 #26161

racepassage
Participant

Removed my old tank and had replacement s/s tank fabricated by the CocaCola Plant maintenance shop in La Paz, Mexico (US$ 125.00).
It is installed against the hull behind a longitudinal ‘mini’ bulkhead over the port side of the port side cockpit locker fuel tank and services the after head. (There is still plenty of access to the tank filler cap).
The ‘Y’ valve and hand pump is in and accessed from the forward locker in the aft head with the through deck vacuum discharge hose leading from the tank, through the locker transverse bulkhead to an overhead fitting on deck.
It all seems to work and it’s out of the way.
Cheers
Roger.

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