Making/installing gravity holding tank

[elias]

Hi to all ,
Once again I want to seek advice in your collective wisdom !
I want to install a new holding tank
1. To empty with gravity
2. Wall mounted
3. 40 liters

So I was thinking this https://www.nuovarade.com/product.php?productId=5565&categoryId=221

To wall mount it with the cap facing outwards and to low height.
My concerns are
1. Will this big round lid leak in the future ( because is designed as a cap i think , not to be in water pressure .
2. Is it a problem that is made for water and not for waste ?
3. Because the lid isnt at the end bottom , after some use solids will build at the bottom or not?

My next idea is to find a simple water tank and drill the hoses appropriate, but how trustworthy can be the drills of a person with limited skills?

[Symphony]

That is not suitable. You need a proper vertical holding tank such as the Vetus Type WW or the Tek Tanks Type A vertical. However it is unlikely that you will be able to fit one in the locker in the loo compartment as they come in standard sizes, although they will fit on a plain bulkhead in a cockpit locker for example. These tanks with fittings are typically between £3-400. A custom tank to fit in the locker (such as I had made for my 37) will cost roughly twice that.

Unfortunately there are no short cuts in doing this job - you have to buy the right kit.

[elias]

Thanks Symphony, but do you think that if I fit one regular plastic water tank can I drill and install fittings myself?

[geoff]

I fitted a plastimo 40ltr vertical in my 40cc . It fitted behind the shower wall and works by gravity. Geoff

[Symphony]

Thanks Symphony, but do you think that if I fit one regular plastic water tank can I drill and install fittings myself?

No. Look at the proper tanks and you will see that the fittings are attached to threaded bosses welded onto the tanks. You want an absolutely secure, odour free connection and this achieved by either welding (or moulding) fixed spigots to attach clamped hoses, or threaded tails with O ring seals if the attachment needs to be adjustable.

As I suggested, there are no short cuts.

[Lazy Pelican]

Symphony is absolutely correct. You need to be 100% certain you have no leaks - ever!
Remember holding tanks do get blocked. The easiest way to clear a minor blockage is to close the sea-cock, pump to pressurise the tank and then open the sea cock. With a bit of luck you hear a big ‘whoosh’ and it’s clear. You need something robust to withstand the pressure.

[elias]

The Plastimo looks that will do the work
https://www.plastimo.com/en/water-on-board/sewage-treatment-device/waste-water-tanks/reservoirs-verticaux-9642.html

[tiger79]

The Plastimo looks that will do the work
https://www.plastimo.com/en/water-on-board/sewage-treatment-device/waste-water-tanks/reservoirs-verticaux-9642.html

Have you considered asking about the same sort of tank which Bavaria would have fitted originally?  It would fit perfectly, and would have the correct fittings sealed on to it.  It may no longer be available, but surely worth asking?

[Symphony]

In 2003 Bavaria were not fitting gravity tanks as standard - at least not in the lockers in the loo compartment. They were either pumped systems with the tank under a bunk or gravity tanks in cockpit lockers as elias already has. He wants to replace that (because it takes up too much space) with a smaller tank in a locker in the loo. That Plastimo tank may fit, but my experience is that standard size tanks don't, hence my suggestion that a custom tank is the way to go.

From what I can see of the Plastimo tank it is not as well made as the Vetus, or particularly the Tek Tanks.

[elias]

My original is in the locker on the back of the stern loo . It is too big for me and I need all the space I can get . Thanks for your help I ll inform what I finally did In the future

[elias]

Found this also , looks rigid
https://www.vetus.com/en/waste-water-systems/tanks-for-waste-water/bulkhead-mounted-waste.html

25liters for 6 persons for one day would be enough no?

[Symphony]

Yes, that is a good quality tank. Are you going to replace your existing tank with this smaller one? That should be enough for one day's use if you limit it to water only - no solids and keep the volume of incoming water to around 6 pumps. It is the flushing water that creates the volume rather than the urine - a typical adult urine volume is less than 500cc, unless they have been drinking heavily. (Because of my medical condition I know more about urine volumes than any sane person should really know!)

[elias]

Yes , I m thinking of the 25 lit or the 60 lit ( there is no 40 in Vetus). I ll use it only for the waste of one loo that is electric . So poo will be around 2 liters per visit that gives around 12 visits... is on the limit ! I ll check the 60lit if is not so space consuming

[elias]

Update

I installed the Vetus W60WW . Very rigid construction . I also put 2 Y valves , cheap , made in Taiwan ,before and after the tank to have the chance to bypass even when full. Thanks for all !