Holding tank seacock location.

[Sitesurfer]

B36 2003, retro fitting a holding tank with an electric toilet plumbed into fresh water.
Planning on a tek tanks 60L mounted in the lazarette wall (facing into the locker) which I believe is where they were mounted, can I clarify whether we use the existing 38mm seacock under the sink (two cabin aft heads) or whether it’s better to retrofit a 50mm new through hull directly under the tank and glass the old one up?

[Yngmar]

38mm should be fine, that's the standard size in our factory fitted tank. Ours gravity drains fine. With fresh water you should have even less problems due to reduced calcium buildup.

I know from a friend who has 50mm outlets that this size hose is very difficult to come by in places, so if you do decide to fit it, carry enough spare hose aboard.

[Symphony]

If you are making a simple gravity installation where everything goes through the tank then use the existing outlet 38mm seacock. Think of the tank as just part of the hose. Leave the seacock open if you want to discharge straight into the sea or shut it if you want to use the tank. Suggest you replace all the hose with sanitary grade which is not only less permeable to potential smells but more flexible, easing installation.

[Sitesurfer]

I have changed the hose to the saniflow butyl stuff which was super easy to work with.

Am I right with the location of the tank? The drawings from Bavaria are a touch vague (at one stage they show the tank as a seat in the locker).
And - just to confirm, Bavarias drawings show the seacocks to be located behind the head/toilet itself, whilst mine is located under the sink unit - this same diagram however also shows the freshwater pump under the sink unit and not (as on mine) under the aft cabin bed so I'm none the wiser!

I would imagine that I can remove the existing anti-siphon loop (which is just a huge loop in the sanitary outlet hose) because this effectively is taken care of with the tank in the system (as in its above the water line etc) which will decrease the amount of distance that the effluent has to travel from the tank to the outlet.

I suspect that I need to replace the 90-degree hosetail on the tru design seacock with a 120 degree as well in order to shallow out the whole run or is this an unnecessary step?

[Symphony]

Yes, the tank is effectively an anti syphon because of the vent from the tank. As to location, it needs to be as high as possible consistent with gaining access to any inspection hatch or fittings on the top. A 120 elbow would be a good idea if there is room. The constraint is usually height for the hose to run to the bottom of the tank. Presumably you will have to make holes in the bulkhead for the pipes and you need to get a straight drop from the outlet to the tank then a smooth bend in the pipe before it goes through the bulkhead. This may mean it comes out too low to meet a 120 elbow on the seacock. Lots of head scratching and measuring before you commit.

[Keweetoo]

Hi Sitesurfer
I have  a Bavaria 35E yr 2000 with a Tec Tanks 60L holding tank mounted in the lazerette directly behind the heads compartment which sounds similar to what you are proposing. The tank is mounted on a timber framework with the gravity outlet back down to the original seacock located under the sink via a cutout in the bulkhead. I can post some photos at weekend if it helps.

[nightowle]

Hi Sitesurfer
I have  a Bavaria 35E yr 2000 with a Tec Tanks 60L holding tank mounted in the lazerette directly behind the heads compartment which sounds similar to what you are proposing. The tank is mounted on a timber framework with the gravity outlet back down to the original seacock located under the sink via a cutout in the bulkhead. I can post some photos at weekend if it helps.

Keweetoo,

I have a '99 35E with a similar setup.  We also have a macerator at the holding tank and I'm not sure if that is needed to be operational to dump the tank out the seacock under the sink, or can I just turn the "y" valve that is also under the sink to the "sea" position and open the seacock.....will that dump the tank or only dump what's in the toilet?

[Keweetoo]

Nightowle,
I'm not sure how the macerator works as we don't have one. On our set-up the heads pump to the holding tank only. Opening the seacock dumps the contents of the holding tank by gravity.

Normally the 'Y' valve will divert either from the toilet directly to sea (providing the seacock is also open -sea position); Or closing the 'Y' valve will divert to the holding tank (seacock closed to 'hold' contents in the tank). When in this position if you open the seacock the holding tank would normally then empty under gravity.

If unsure you could always experiment with some food dye.

[Symphony]

You are right about the purpose of the Y valve, although this is not often used now on gravity systems for simplicity. Where it is essential is when a pumped system is used as was fitted on some earlier Bavarias. This has a separate holding tank, usually under a berth so below the waterline and you can either send the waste to the tank or directly overboard. Often these systems have their own seacock, sometimes with a 1" outlet and macerator is used to chop up the waste to a slurry before it is pumped out. This type was an option on my 2001 37 but the tank was on the opposite side of the boat under the saloon berth about 4m away from the toilet. The thought of a 4m hose full of waste running under the saloon did not appeal so I did not specify it and instead fitted a gravity tank.

No holding tank is ideal but the simple basic gravity installation is pretty idiot proof if kept clean so deposits do not build up over time.