Toilet waste tanks - fittings again!

[stuart]

Looking at getting a custom steel tank built for the waste. Needs to be an "L" shape to fit the location we have on the boat but this should not be too much of a problem.

 

Would it help if it were galvanised to avoid rusting though?

What thickness of steel would you recommend?

 

I'm also getting a little confused with the pipe connections/vents to the tank.

 

What I think we need is:

* 38mm Pump out fitting and pipe (this will be on the cabin roof)

* 38mm Vent to below gunwhale level on side of boat but above the tank (this will be always open to the air and basically just a pump out fitting without the cap on!)

* 19mm Rinse out fitting (also on roof)

 

I'm aware that the pipe work will need to be the special stuff to stop smells coming through it.

 

I like the idea of the vent below the gunwhale to avoid the bad "curry smells" wafting into my face while I'm steering

 

Does this make sense?

Edited April 14, 2005 by stuart

[John Orentas]

Stuart.

 

Make the tank as thick as you reasonably can, 5 or 6mm. Don't make the design too intricate remember the solid can separate and remain in awkward corners.

 

Maximise the volume, take the tank through the floor and down to the bottom plate, pump outs are a fixed price. Galvanising, can be a problem whether hot dip or electroplate, not many places will tackle such big units, but un-painted they will last for a very long time (they say the steel pickles, whatever that means).

 

Remember the pump, out pipe, 38mm needs to pass through the tank to about 1 inch from the bottom, the same vent just welded in the top with the fitting best on top of the gunwale it can also double as the rinse inlet.

[stuart]

It will be difficult to get the tank flat onto the base plate as theres a floor bearer right in the way. I'd like to use an "L" shape to make the most use of space and allows me to put the tank partly under the bed as well.

 

I have removed the wooden floor so thats given me about 40mm more height, and will put a solid wooden structure below the floor to sit the tank on.

 

Should have given it a bit more thought when I designed the layout of the boat and got Liv.Boats to move the bearer further apart in the bathroom area - too late now!

 

 

Did you suggest that the vent would be better above or below the gunwhale?

 

What about baffles in the tank - anyone bother? Notice that the lee san. tanks have these fitted but they are plastic.

Edited April 14, 2005 by stuart

[John Orentas]

Stuart.

 

I would suggest the vent should go on top of the gunwale, or as you are already piping up to the roof you may as well make it a pair. Remember also, the more of the tank you can get toward the middle of the boat the less trouble you will have with trim.

 

You don't need baffles, if the plastic tanks have them they are probably more to do with stiffening.

[Alastair]

Erm, I've read (in several places) that black water tanks should be plastic, never stainless. Something to do with the SS not being, erm, stainless, in anaerobic conditions.

There is a chap on the Yachting world forum who has just had his SS tank rust through.

[stuart]

Erm, I've read (in several places) that black water tanks should be plastic, never stainless.  Something to do with the SS not being, erm, stainless, in anaerobic conditions.

There is a chap on the Yachting world forum who has just had his SS tank rust through.

<{POST_SNAPBACK}>

 

I was just thinking of mild steel, not stainless....

[Jus73]

Hi Stuart

 

38mm for the vent is fairly big, the vent on my pump out is 16mm. This is situated below the gunwhale.

 

If you're concerned about smells you could always fit a 'No-smell' filter (Vetus do various sizes). I've never noticed any nasty smells from the vent even without the filter, although i do have a small 215ltr plastic Vetus tank that is emptied often.

 

Justin.

[Big COL]

Hi Stuart

 

38mm for the vent is fairly big, the vent on my pump out is 16mm. This is situated below the gunwhale.

 

If you're concerned about smells you could always fit a 'No-smell' filter (Vetus do various sizes). I've never noticed any nasty smells from the vent even without the filter, although i do have a small 215ltr plastic Vetus tank that is emptied often.

 

Justin.

<{POST_SNAPBACK}>

 

Hi Stuart

 

The vent should be 38mm the same size as the pump out. I am told this is to enable equal pressure to be maintained when having a pump out. I would fit the vent under the gun whale to avoid any smells straight into your face when on the move. You will still probably get a whiff from it even with it under the gun whale, but you can always fit a filter later if this is a nuisance

Edited April 14, 2005 by Big COL

[Alastair]

I don't think mild steel would be much better.

 

Blackwater tanks are usually plastic, these days. Try Tek tanks

[Richard Bustens]

Hi

Any more comments about s/steel for black water?

 

I have just fitted a 100 gall one under the boatman's cabin

[Gary Peacock]

Somwhere around 6mm plain steel untreated inside no baffles with an inspection hatch with a very good seal. (I personally will not be opening it however much you offer to pay, some one did ask once but the offer was quickly declined.)

 

Lee sanitation do a nice range of plastic ones two.

 

 

Gary

[David]

Hi

I'm new this week week, but made my own stainlees steel pump out tank 36 years and three boats ago, one eighth sheet MMA welded (manual metal arc or "stick" welded) the boat is still around and the tank is still OK the owners tell me. Mild steel in 6mm will still last longer than the rest of the boat and be cheaper. One thing none of the other good advice mentioned was make sure your vacuum pipe is located at the low end of the tank, i.e. most boats trim stern down so have the pipe to the stern end of the tank, in fact if you have it made to specification have it made with a small fall or slope also toward the stern any fabricator worth using can arrange the plate to do that. The pump out than picks up more of the effluent before sucking air and the solids gravitate toward the pipe better.

Just a thought in all my years of boating when ever you get two or more boaters talking while waiting for locks or watering up etc you can almost always end up at some point talking pumpouts or potties !!!

David

[Richard Bustens]

Ar David .

Now that i did not think about, and the inlet, outlet pipes are at the bow end of the tank, coz the pipe run was less, spose that means 1-2 galls left in after pumping out.

[Alan Saunders]

I am in the process of moving a 100 gallon stainless steel holding tank. If the tank material is the same as the inspection hatch it is only 2.5mm thick. It is 20 years old and has not corroded through - yet. Anyone know where I borrow or hire an ultrasonic thickness tester?

 

Lee Sanitation say that the vent needs to be big enough to allow aerobic conditions. Their website is a bit confusing because they first say that the area of the vent should be at least 38mm (only 7mm diameter) then later say you should use 38mm pipe for the vent. They also imply that the reason for not taking the vent higher than the gunwale is to minimise the pressure on the tank should it be overfilled. I guess they are thinking of boats that are a bit taller than a canal boat.

 

My tank had a 22mm copper vent. It looks like the tank has been overfilled in the past. The horizontal section near the tank was lined with a quarter inch of scale and had corroded through.

 

I like the idea of using the rinse-out as the vent but I wonder why Lee Sanitation don't suggest it. I guess the problem is that the the rinse-out water from a good hose will not run freely without a separate vent? Is a ventilated rinse-out cap available?

 

Stuart, make sure the tank will fit through the doors, past the cratch etc. In 6mm steel it is going to be heavy. A 60 gallon, 4'x2.5'x1' tank in 6mm steel will be almost 3cwt (150kg) unless I've slipped a decimal place somewhere

 

Alan

[dor]

I've got a fairly largish holding tank, with pumpout & vent pipe going to the top of the gunwale. The vent pipe is labelled "rinse", but the cap has holes in it. I have yet to have a pumpout where the rinse plug has been removed - they all seem to pump out for a while, then put a hose in the pumpout pipe while they find the blue, then pump out the rest. Seems to work.

 

Although the previous owner fitted a Vetus "no-smell" filter, with a vent through the side of the baot just above the gunwale, It has never been fitted with a filter. If you look at the price of a pack of filters you will know why.

 

By judicious use of hedges & pubs, I contribute very little "liquid" to the tank. I haven't managed to persuade my wife to use the hedge yet. So although we hgo out on the boat virtually every weekend, it is usually several months between pumpouts.

 

Either I am immune to it, or three is not a lot of smell coming from either the unfiltered vent pipe or the "rinse" vent pipe.

 

They also imply that the reason for not taking the vent higher than the gunwale is to minimise the pressure on the tank should it be overfilled

- surely if the tank was filled higher than the gunwale, the contents would be pouring out of the toilet pan? Can't see how taking the pipe up to the roof is a problem - I think it is quite common on hire boats as it makes it easy to pump out from either side.

[Alan Saunders]

. . .  - surely if the tank was filled higher than the gunwale, the contents would be pouring out of the toilet pan?  Can't see how taking the pipe up to the roof is a problem - I think it is quite common on hire boats as it makes it easy to pump out from either side.

<{POST_SNAPBACK}>

Yes that's what I thought too thinking only of a 'dump-through'. If you had a loo with a macerator pump and a remote tank you could probably fill it to several times the test pressure.

 

The Lee Sanitation web page Holding Tanks says:

 

"Standards call for an installed pressure test. Our tanks are pressure tested allowing for a vent rising 2m (6'6") above the tank. Vents should not rise above this height and ideally breath through the hull side below the gunwale."

 

"We strongly recommend, wherever possible, a full permanently opened 38mm ID vent as the preferred option. This allows both the discharge of displaced air and the free flow of air in, to retain the effluent in an aerobic condition. Tanks with small breathers will almost certainly turn anaerobic. It is in this latter condition, created by the absence of oxygen, that malodours occur."

 

A vent in the roof of a narrowboat is OK. The shorter the vent pipe the better the ventilation.

 

I don't understand the references to aerobic conditions; I thought the formaldehyde in the 'blue' prevented aerobic decomposition. Perhaps they don't use 'blue'?

 

Alan

[rog guiver]

I was going to comment that our new tank uses the baseplate as its bottom but that might take this topic "off-topic". It has allowed the tank to go under the floor of the passageway and hence keep it more central to the boats centreline and increase its capacity (the volume under the passageway being 4*24*72 inches, with the main part of the tank being 10*36*72 inches)

 

What is worth considering, apart from the vent pipe (where we have a fan that runs during the "dump cycle" of the mansfield and stops "nasty" smells entering the bathroom) and the rinse out (at the front of the tank with the skin fitting in the centre of the roof) is to have two pumpout points at the rear of the tank, one to port and the other to starboard!

 

This saves the question.. Why is it is always raining when the pumpout point is not on the bank-side??

Edited April 18, 2005 by rog guiver

[Heron boats]

Stuart,

If it is to be a mansfield dump through toilet then I would recomend routing the suction pipe inside the tank to be directly below the toilet bowl.

With these types of toilets it is possible to get a heaping effect directly where the waste lands, especially if (as is often the case) you try to limit how much water you flush away.

With the suction pipe under the bowl you will suck out all the solids first, ensuring that the tank is empty, if the pipe was situated in the corner of the tank, possibly several feet away there would be a risk of pumping out the fluid and leaving the solids behind.

We have done our tanks this way for years and it works well, its more work but it beats having problems in such an unpleasant area!

 

Ignore the above if its to ba a mascerator of course!

[Big COL]

Stuart,

If it is to be a mansfield dump through toilet then I would recomend routing the suction pipe inside the tank to be directly below the toilet bowl.

With these types of toilets it is possible to get a heaping effect directly where the waste lands, especially if (as is often the case) you try to limit how much water you flush away.

With the suction pipe under the bowl you will suck out all the solids first, ensuring that the tank is empty, if the pipe was situated in the corner of the tank, possibly several feet away there would be a risk of pumping out the fluid and leaving the solids behind.

We have done our tanks this way for years and it works well, its more work but it beats having problems in such an unpleasant area! 

 

Ignore the above if its to ba a mascerator of course!

<{POST_SNAPBACK}>

 

 

To clean a tank throughly if using a Mansfield toilet you can rinse out through the toilet, open the flap an you can see any solids left. You have to suffer a little bit of Satan's breath, not too bad when the tanks empty but at least you can get it clean.

[Guest]

Hi All. Can you help us out ? To avoid further argument ! We are fitting a drop through toilet. We will use a plastic tank. The design would be best as an l shape. My husband thinks an l shape is too complicated and you would get waste stuck. If we don't go for l shape it means straddling two rooms and messing up the bathroom design. 

Can you help me ?!! 

[Alan de Enfield]

4 minutes ago, MrshappyH said:

Hi All. Can you help us out ? To avoid further argument ! We are fitting a drop through toilet. We will use a plastic tank. The design would be best as an l shape. My husband thinks an l shape is too complicated and you would get waste stuck. If we don't go for l shape it means straddling two rooms and messing up the bathroom design. 

Can you help me ?!! 

 

Cube or nothing.

[Tonka]

7 minutes ago, MrshappyH said:

Hi All. Can you help us out ? To avoid further argument ! We are fitting a drop through toilet. We will use a plastic tank. The design would be best as an l shape. My husband thinks an l shape is too complicated and you would get waste stuck. If we don't go for l shape it means straddling two rooms and messing up the bathroom design. 

Can you help me ?!! 

What is next to the bathroom ? If it is a dinette seat or bedroom then the tank will fit under the bed/seat and under the toilet

[magnetman]

Cuboid (rectangluar box shape).

If it is a dump through unit being installed then due consideration and design of tank vents is important.

 

I know people do put vents in but air will find the easiest route out so if the flap in the lavatory itself is larger than the total of the vents thats where it will probably come out.

 

 

Edited December 21, 2023 by magnetman
stimulus

[Guest]

We are taking this seriously! So we are now thinking a wedge shape ... Worked out the capacity to be 129.6 litres running along the back of the bathroom wall. It would be 5" at it's thinnest and over a foot at the toilet end. 

17 minutes ago, Tonka said:

What is next to the bathroom ? If it is a dinette seat or bedroom then the tank will fit under the bed/seat and under the toilet

Our wardrobe.  Not willing to risk the smells tbh and just want everything contained in one room ! 

18 minutes ago, magnetman said:

Cuboid (rectangluar box shape).

If it is a dump through unit being installed then due consideration and design of tank vents is important.

 

I know people do put vents in but air will find the easiest route out so if the flap in the lavatory itself is larger than the total of the vents thats where it will probably come out.

 

 

Ok great point and we will definitely be looking at more rectangular shape 

[Bobbybass]

With the use of white vinegar to clean the loo....plus the acidic nature of certain " secretions".... my thick mild steel tank rotted through in 8 years.