Bavaria 40 (J&J) forward holding tank

[MagicalArmchair]

The one place that might be challenging to go into in marinas with social distancing at the moment, will be the ablutions block. We have a shower on board and that kind of grey water should be fine in tidal marinas, however, we do not have a holding tank. I've been meaning to fit one to Mirage as I do fancy Holland now the kids can ride their bikes, however, it hasn't been high on my list of projects until now.

Has anyone had any experiance of fitting a holding tank or any advice from their own adventures in this area? I'm favouring the kind of build below - simple with a minimum of moving parts:

https://www.sailmagazine.com/diy/boatworks-holding-tank-set-up

I haven't got a picture of Mirages heads, however, its as the below (borrowed) photo. That locker over the heads looks a likely candidate to hold the tank (as it would need to be over the waterline).

[Symphony]

Yes, a gravity tank such as the one in the link is the simplest and much like the system fitted to later Bavarias (and most other production boats). The difficulty with retrofitting is first finding enough space to fit a decent size tank - typically you want to aim at 40l minimum - and then getting a tank to fit the space maximizing the volume. On my 37 which had a similar locker to yours I managed to fit a 45l tank, custom made to fit the space. it was a very tight fit and we had to move the domestic water pump and changeover valves a bit, but it worked very well. You can buy ready made gravity tanks, but unlikely you will find one that both fits and gives you a good volume.

You will find lots of good information on designing tanks on www.tek-tanks.com who manufacture custom tanks and sell ready made tanks. They may well have already made a tank for your layout, but if not will design and make one for you. They have made two tanks for me in the past, one a holding tank and the other a water tank. I made a full size mock up in hardboard and they did the layout of pipes, fittings and attachment points. Not cheap, but excellent quality. Went through the same process for the one in my 37 but in Corfu with a guy who used the same sort of materials and manufacturing process.

Make sure in the design that your access hatch for cleaning allows you to get to the outlet for rodding as this is the most common place for blockages, although if you avoid leaving waste in the tank, as well as minimising the amount of solids (paper etc) you put through the tank you should not experience blockages. My routine is to leave the tank empty and the seacock open all the time except when I want to use the tank. I then empty it as soon as I am in open water (or using a pumpout) and also pump some freshwater through the whole system.

Well worth replacing all the hose with butyl as I expect you will find the existing hose stiff and lined with deposits. Butyl is not only less permeable, but is more flexible - i expect your new pipe runs will be quite tight!

Good luck with the project. It is not easy or cheap and you don't get the satisfaction of being able to constantly admire your handiwork. Revarnishing a saloon table for example is much better value for your money and effort in this respect.

[sy_Anniina]

As owners of (J&J) Bavaria 40 aft-cockpit, the photo looks like the heads next to companionway. On our boat the gravity holding tank is located at the locker above the toilet seat.

We have also considered a forward holding tank but have not yet managed to make the crucial decision which storage space to sacrifice: locker above the toilet seat, under saloon settee, or forward cabin stbd lower cupboar / locker (and the latter two without gravity discharge). For further consideration - on some crew setups, the Admiral might not like the idea of holding tank in fwd cabin or saloon

BR,

Tommi
s/y Anniina

[MagicalArmchair]

Thanks for the feedback Symphony, I've sent the email away to TekTanks. How long did the fitting process take in man hour of fitting? Guessing you made up a template from MDF to make sure you could menouver it in? I'm also guessing the fabrication at TekTanks will take a while. Total cost of project also? £1,000 for the tank itself? I know TekTanks aint cheap (beats the contents escaping mind you!)!

You are quite right, that is the aft heads - the forward heads is the below. (Shows how much I've been able to see my new boat!). There is still a locker above that guy, that might be the place to put our holding tank.



As for varnishing - the one thing I really miss from my old boat was the tiller. There is something spiritual about sitting in the sun, varnishing your tiller on a still and windless day.

[Symphony]

The 2 tanks I had made by Tek-Tanks were on my old Eventide and were in a location where a hard mock up was easy. With the 37 the guy who made it used cardboard and masking tape (and a lot of swearing in German!), then cut out the panels and tried them before welding up. He was used to making them so did it accurately in a fraction of time it would have taken me.

I would think £1000 would cover all the materials. Not had a quote for a few years, but in 2009 the tank cost around £400. As there are no pumps involved the only other parts you need are hose, clamps and a deck pumpout fitting.

[MagicalArmchair]

Thanks Symphony, I'll lay it all out on a piece of 'paper' and post it up here for comment.