Critique my holding tank system design please

[elaak]

Originally Posted by peghall

You keep trying to over-complicate it.

Get rid of the "sag" in the toilet discharge line...run the line straight uphill to the tank. Your toilet can move bowl contents up to 6' in the dry mode. No vented loop is needed. Eliminate the direct overboard flush from the toilet...send everything to the tank. When at sea, leave the tank discharge thru-hull open.

Eliminate the pressurized fresh water flush option...manual toilets do not have the built-in protections to prevent contaminating your fresh water supply with sea water. Instead, disconnect your toilet intake line from its thru-hull and re-route it to tee into your head sink drain line. That will provide a safe source of fresh water (the sink) to rinse the sea water out of your system. Tee needs to be below waterline as close to the seacock as possible. To rinse, close the sink drain seacock, fill the sink with CLEAN fresh water, flush the toilet. I can give you the details separately.


Finally, we prob'ly should discuss the best location for your tank. Ronco Plastics is your best source...they make top quality tanks for a very reasonable price and have more than 400 shapes and sizes, including at least 100 non-rectangular...and they install fittings in the sizes and locations specified by the customer when they make the tank. There are retailers who sell Ronco tanks, but Ronco sells direct for a much lower price...and they're great to work with. Ronco Plastics marine Tanks

Their tank drawings are here: Ronco Plastics tank drawings When looking at drawings it's important to know that there is no top or bottom until the fittings go in, and YOU decide where they go. So rotate, flip in any orientation to find the tank that fit your space.


--Peggie

Thanks for the feedback Peggie.

I wish I could eliminate the sag but alas. The most desirable location for the holding tank is on the other side of the hull from the head (narrow catamaran hull) and so the hose has to go under the sole. The sink is also a pretty far jaunt away (3m further forward). Is the sag worth considering the current installation location a no-go?

Thanks for the tank vendor tip! Have just starting reaching out!

[mitiempo]

Originally Posted by elaak

Thanks for the feedback Peggie.

I wish I could eliminate the sag but alas. The most desirable location for the holding tank is on the other side of the hull from the head (narrow catamaran hull) and so the hose has to go under the sole.

For a reliable system install the tank on the same side as the head, behind it and higher.

Your design is not reliable.

[elaak]

If I could I would, but alas...my vessel lacks space to do so without some major compromises in its own right.

My goal is to understand which compromises are the right ones to make and what can be done to defeat the compromises of any given installation. As we all know, with a marine vessel in tight spaces sometimes compromises have to be made.

In this case the sag in the pipe, and lack of easy access to fresh water are about the only things left.

[mvweebles]

I don't understand - both "KISS" and OP original design require the holding tank to be above waterline in order to avoid a vented loop. The OP-design has a lot more hose and a Y-valve - all of which take up a lot of space. Of course, if OP is planing to mount tank below waterline, there really needs to be a vented loop on the hose shown at bottom of tank to thru-hull. Would be a really bad idea to leave this out just to get gravity feed ("Hey Fred, I heard your boat sank at your slip - tough break!!!" "Yea, I don't understand it - only this past weekend I was working on the head and everything looked great when I left....")

Freshwater flush is a different matter - when I had a saltwater head (Groco Model K), I kept a small plastic container in the head and would rinse the bowl with a quart or two of fresh water after a flush.

Sounds like you've made-up your mind to go with your original design vs consider the KISS design. Just curious why - maybe I missed something.

Regardless, good luck

Peter

[mitiempo]

Originally Posted by mvweebles

Of course, if OP is planning to mount tank below waterline, there really needs to be a vented loop on the hose shown at bottom of tank to thru-hull. Would be a really bad idea to leave this out just to get gravity feed.....

Peter

A vented loop below the waterline is a good way to sink a boat - they have to be mounted above the heeled waterline a ways.

If the tank is below the waterline gravity drain will not work.

[elaak]

Originally Posted by mvweebles

I don't understand - both "KISS" and OP original design require the holding tank to be above waterline in order to avoid a vented loop. The OP-design has a lot more hose and a Y-valve - all of which take up a lot of space.

Freshwater flush is a different matter - when I had a saltwater head Groco Model K), I kept a small plastic container in the head and would rinse the boat with a quart or two of fresh water after a flush.

Sounds like you've made-up your mind to go with your original design vs consider the KISS design. Just curious why - maybe I missed something.

Regardless, good luck

Peter

I think you might have because missed something. The v2 drawing is essentially a match for the KISS system with the exception of the direct overboard Y-Valve option as far as discharge is concerned.

I was under the impression that saltwater through a holding tank system was a no-no so I was giving myself an option to revert to a minimalist even more KISS option when a holding tank was not needed. To be clear, the vented loop and skin fitting for direct discharge all exists already. Sounds like saltwater through the holding tank system is quite common though so happy to give the holding tank pass through a shot.

For freshwater, I’ve got some options in mind for how to access it. Either running a very long hose to the sink or installing a showerhead at the head.

The other exception is the pipe sag. While I’m very happy we all live in an ivory tower of holding tank installations, I suspect in common practice the runs aren’t always quite as ideal as they always appear on the example drawings.

Anyone have a gravity installation where there is a bit of pipe sag to below the level of the head? Perhaps 20cm?

Cheers

[mvweebles]

Originally Posted by mitiempo

A vented loop below the waterline is a good way to sink a boat - they have to be mounted above the heeled waterline a ways.



If the tank is below the waterline gravity drain will not work.

Poorly worded on my part, but we are saying same thing.

But question remains: what problem does your original design solve that the KISS one does not?

Peter

[goboatingnow]

I would avoid wherever possible two things

Long pipe runs
Pipe sag , ie any significant length where the pipe remains both below the toilet and the holding tank.

Both will lead to accumulations , and calcification ,and will be a repository for smells. Long runs increase the chance of blockages and the difficulty of clearing them

Redesign the physical space to place the holding tank near and above the toilet , I’d even suggest using a very small tank , good for a day or two if push comes to shove. Beneteau managed to fit them in the wet locker !

Discharge through the tank , Y valves are a nightmare ( and illegal / frowned upon in many jurisdictions )

[SailMoonShadow]

Originally Posted by sail sfbay

Holding tank above the toilet will not work UNLESS you install a lift pump on the toilet outlet to a high point above the holding tank with gravity flow from the high point to the holding tank.

Not true!
I installed a holding tank on my 1989 Sigma last winter. The tank is well above the toilet but the top is not quite as high as the vented loop was previously. I've had no issues at all.

[barryglewis]

Originally Posted by Cheechako

Pump the poop from the toilet into the top of the tank.
Do not intersect it with the Tee on the bottom.
Have it drain direct to a thru hull close by.
You could eliminate the overboard discharge you show from the toilet and pump, send everything through the tank, even if you then drain it to the sea. (Assuming you know your gravity is going to work, mine did) KISS

We did this with Risky Business in 2014. We use a Jabsco electric toilet.
Our set-up has an extra valve just under the tank, which we have never used.
Has worked ok for abt 50,000naut miles.
The main improvement we could make is a way to check how full the tank is!

We flush only with saltwater, but copiously. Also get men to use a passport. This and Lots of flushing keep away smells.

[barryglewis]

Sorry, for passport read pisspot!

[malbert73]

After overflowing our last holding tank into the bilge via an inspection port that leaked, we added the full sensor that interfaces with our raritan elegance and locks out the auto flush cycles if it’s full.
But, it doesn’t give us warning we are getting close to needing pump out so we also added the SCAD technologies external tank sensor on our new Ronco tank. It works really well with external foil strips

[robochef]

Check this website out. It has several head configurations!


https://www.tek-tanks.com/sanitation...g-and-layouts/

[Dr.No]

In redesigning from two head compartments to one, I used pretty much the exact system that Nigel Calder has in his book, except that the elevated tank is not on centerline I’m using one of the existing Jabsco Electric toilets with a 1” hose to the top of a 50 gallon Vetus polypropylene tank that is right under the deck. The tank has a vent to the other side of the boat, a pump out port directly overhead, and a 3 or 4 foot 2” hose with 2” Marelon seacocks, one under the tank, the other through the hull. The head is supplied by a separate 15 gallon bulkhead mounted Vetus tank. These changes eliminated 5 seacocks! The system is incredibly simple. We will see how it works fairly soon. Cheers!