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Old 11-01-2013, 09:02   #1
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design and layout a 2 Head System for a new build

Hi folks

I am seeking some design help for a 2-Head system on a new build 40' steel trawler. We are starting from scratch here so we need everything, from heads, to pumps, to tanks, and all the HOW-TO'S for laying out this system.
Photos or drawings and whatever help you can forward along would be greatly appreciated.

Thank you
Capt Nemo
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Old 11-01-2013, 09:20   #2
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Re: design and layout a 2 Head System for a new build

I'm in the same boat (so to speak). So I'll be interested to see any ideas also.
Matt
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Old 11-01-2013, 09:24   #3
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Re: design and layout a 2 Head System for a new build

I would think that just about everything in building a new yacht would be more complex than the head system. My thoughts though. Only use 1 tank and make it as large as possible at least 40 gallons, more if you have room. Use a very high quality pump ($500) to pump overboard, have it connected to the bottom of tank so its always primed, and put a valve between so it can be serviced when tank is full. Dont do fresh water flush unless you have a watermaker, even then have a separate water tank">fresh water tank for heads, and a Y-valve so you can use saltwater flush if needed. Also maybe 2 heads is overkill on a 40' boat if its just 2 out doing exstensive cruising.
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Old 11-01-2013, 10:07   #4
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Re: design and layout a 2 Head System for a new build

These are the guys to buy your tank from: Ronco Plastics - Marine Water Tanks, RV Water Tank, Auto Detail Tanks, Water Tanks
They have a huge selection of shapes and sizes. Their tanks are heavy walled and they will put the fittings anywhere on the tank you want them.

Another suggestion would be to use a larger than normal vent. The more air circulation you can get into the tank the less it will smell. The bigger the vent the less likely it is to get blocked as well. Normal is 5/8" ID. Try going up to 3/4" or 1".

Have you decided on toilets yet? Raritan Elegance have been getting rave reviews lately. They can also be set up to flush with fresh water from your tanks or switch to raw water if fresh is in short supply.

Raritan also makes a sanitation hose that is guaranteed for five years not to smell. It is also very flexible which makes installation easier. Trident also makes a very good sanitation hose but it is not as flexible.

I'd love the opportunity to quote you on your toilets. We're distributors for Raritan, Jabsco and Groco.
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Old 11-01-2013, 10:08   #5
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Re: design and layout a 2 Head System for a new build

I had a 40' steel trawler and had enough room to put in a plastic tank the size of a 55 gallon drum. The head sat right on top and was gravity fed into the tank. Same setup as recommended for pumpout.
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Old 11-01-2013, 10:19   #6
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Re: design and layout a 2 Head System for a new build

I think the ultimate two-head system is one that is plumbed directly overboard only, and on that is a composting toilet.

Easy, inexpensive, and versatile.

Chris
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Old 11-01-2013, 10:24   #7
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Re: design and layout a 2 Head System for a new build

Marine Sanitation Systems - some system design alternatives
System Design
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Old 11-01-2013, 10:30   #8
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Re: design and layout a 2 Head System for a new build

I would have two tanks with two heads. The idea of one tank, as mentioned above, is wrought with difficulties, mainly in hose runs and hoses have to be replaced every so often. In addition any problems (and,sooner or later, you will have some) will be very difficult to resolve with long hose runs. I assume that the heads will be a fair distance apart.

Holding tanks come in many sizes and your best bet is too have the tank as close to the head as possible. If you have a chance, go aboard a 40 foot Beneteau and check out their approach to two heads and holding tanks. Very well thought out. You can put a large tank near the head you will use most often and a smaller tank in the other one.

I have two heads in my 39 footer and, believe me, the second head has come in useful.
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Old 11-01-2013, 10:42   #9
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Re: design and layout a 2 Head System for a new build

[QUOTE=Vasco;1127557]I would have two tanks with two heads. The idea of one tank, as mentioned above, is wrought with difficulties, mainly in hose runs and hoses have to be replaced every so often. In addition any problems (and,sooner or later, you will have some) will be very difficult to resolve with long hose runs. I assume that the heads will be a fair distance apart.

I agree totally.
1)Your tanks can be custom made for about the same price as standard tanks... and they will be better tanks. A small custom one I had done was $90 and was 3/8 thick plastic.
2) if the tanks are well above water line (which they might be in a trawler) Just have the head always pump into the tank and have the outlet on the bottom of the tank. You can gravity dump whenever you open the seacock. No pumps etc to deal with. Simple effective and easy. If possible, design your tanks for "vertical" storage (ie: long and tall instead of low and flat) Mine was bulkhead mounted with the bottom near waterline. It emptied quickly and well. If they are not above waterline or cant fit vertical tanks you may need a pump.
3) All seacocks are not created equal; look at the actual bore size inside. Some are quite small/restrictive for the size specified.
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Old 11-01-2013, 10:57   #10
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Re: design and layout a 2 Head System for a new build

2 Tanks would mean 2 different deck pumpouts or a y-valve and a long hose run to each tank. Long hose runs dont bother me in the least. Gravity pumpless draining is the way to go if it can be set up, but I wouldnt build my boat around it. Useing a pump to empty tanks isnt the end of the world.
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Old 11-01-2013, 12:19   #11
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Re: design and layout a 2 Head System for a new build

Quote:
Originally Posted by RabidRabbit View Post
2 Tanks would mean 2 different deck pumpouts or a y-valve and a long hose run to each tank. Long hose runs dont bother me in the least. Gravity pumpless draining is the way to go if it can be set up, but I wouldnt build my boat around it. Useing a pump to empty tanks isnt the end of the world.

Yes that's how it works. Two deck pumpout fittings. If you've replaced or had to remove sanitation hoses, long runs really complicate the process. Hoses are always behind something or under something or through something. It is never simple and if you can avoid long runs to begin with, that's the way to go. With custom tanks and a blank slate designing a head with short hose runs would be the way to go.
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Old 11-01-2013, 12:48   #12
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Re: design and layout a 2 Head System for a new build

]Having built two boats to my specs. Heres what I do

Separate holding tanks, minimise pipe runs and bends. All sewage systems smell.

Plumb the toilet into the holding tank , no need for Y valves, I would not reccomend any fitting on the bottom of a tank as its under static pressure and inevitably leaks and most likely it will be inaccessible.

Evacuate the tank by electric mascerator pump, I used the large Jabsco versions, plumbed from the top with a drop pipe in the tank. Add a manual vacuum removal pipe also with drop pipe and a flushing water feed pipe. from the deck.

Make sure you have a good inspection access, I now favour appropriate rated plastic tanks as best. Install a good quality cleanable gauge and connect to sensor.

Im a fan of Jabsco , electric macerator toilets, they are loud, but they rarely block and when they do its always just between the bowl and the blades and often fixable from the bowl. Once through the blades theres never any further blockage.

Over size the pipe from the toilet to the tank and ensure no sharp bends ( no 90 degree elbows.

Install a vent pipe and a vent filter from the tank to outside.

You can discharge above or below the waterline, below is best, if the tank is below the water line , use a loop above the waterline then down to the seacock. If both toilet and tank are below , use a vented loop with the vent pipe run overboard. ( though the risk is small as you normally keep the seacocks closed)

Use small quantities daily of chemical toilet fluid, helps dissolve everything and keeps smells down
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Old 11-01-2013, 12:58   #13
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Re: design and layout a 2 Head System for a new build

Quote:
2 Tanks would mean 2 different deck pumpouts or a y-valve and a long hose run to each tank. Long hose runs dont bother me in the least. Gravity pumpless draining is the way to go if it can be set up, but I wouldnt build my boat around it. Useing a pump to empty tanks isnt the end of the world.
After many experiences I wouldn't recommend this , even though its very common on boats like Beneteaus and Jeanneaus.

Firstly long pipe are a serious factor in blockages , as the liquid runs away and the slower moving solids get left behind and cause blockages over time. with a long pipe, you then often have to remove a huge section, as rodding plastic pipes is difficult and risks damage. Often in boats its difficult to get proper falls for long runs.

Gravity fed discharge from holding tanks is problematic, over time sold waste can concentrate in the tanks or just settles to the bottom and can form a difficult to move lump. Equally , especially if using manual toilets, the waste is pumped in as lumps an TP often remains together. Hence gravity discharge tanks in my experience always generate blockages, and the exit pipe needs to be big and its a underwater failure issue.

I would always reccomend , macerator based electric discharge. If your worried about failure, rig a manual backup pump.

equally as I said above , I would recommend macerated input to the holding tank.

dave
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Old 11-01-2013, 13:04   #14
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Re: design and layout a 2 Head System for a new build

Like I said I'm no fan of twin tanks, especially in a 40' boat. Long hose runs dont bother me, and yes I've changed hoses and nasty sewage parts. I would rather just have 1 head to keep it simple, but If I chose to have 2 heads I would still prefer just 1 tank, 1 overboard, and 1 pump.
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Old 11-01-2013, 13:58   #15
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Re: design and layout a 2 Head System for a new build

No need to re-hash the corrosion issues with steel, stainless steel or aluminum waste tanks but polyethylene tanks will eventually degrade to a somewhat more permeable state over time and the different coefficients of expansion/contraction of the different plastic fittings don't help. Even the most expensive "sanitation" grade hose will also become permeable to the waste gases.

Twenty years ago we fitted an FRP waste tank, installed two 1" vent lines (critical) and used ABS piping instead of hose. The only hose we have is a few inches to connect the pipe to the toilet and a few more at the tank. We use the fiber reinforced clear plastic stuff.

Not a wisp of odor for 20 years (15 as a liveaboard).
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