Marine toilets/waste tanks/macerators

[coopec]

I am trying to work out how I will plumb up my toilet/macerator pump/holding tank.

There two systems which seem to be popular but work entirely differently.

Boat Projects

Ericson Yachts

With the Boat Projects system as soon as you've used the toilet you'd press the button to start the macerator pump for a second or so to pump it into the waste tank. Then you'd empty the tank using a diaphragm pump at sea.

Ericson yachts uses the toilet pump to send it to the waste tank or directly out through the skin fitting.

Is anyone aware of the pros and cons of both systems and could express an opinions as to which is best?

Thank you.

Clive

 

[pvb]

I believe the key to having a good relationship with the holding tank is to design it with the maximum simplicity. The fewer valves, bends, pumps, etc, the better.

There is undoubtedly an advantage in being able to pump the toilet straight out to sea if required.

If you can mount the tank above the waterline, gravity discharge means there's no pump needed.

 

[coopec]

I agree 100% with your approach to keeping it simple. Unfortunately my holding tank will be below the waterline.
Thanks

Clive

 

[pvb]

There are some tips in this guide:-

http://www.tek-tanks.com/website/wp-content/uploads/2009/09/Tank-Below-Waterline-Layouts.pdf

 

[MoodySabre]

Mine is below the waterline. There is only one pump and that is a macerator for emptying the tank. The tank empties through a Y connector in to the same seacock as the direct outlet from the pan. A diverter switches between direct and holding tank.

 

[moomba]

Mine is below the waterline. There is only one pump and that is a macerator for emptying the tank. The tank empties through a Y connector in to the same seacock as the direct outlet from the pan. A diverter switches between direct and holding tank.

Exactly what I have done I have used a whale gulper pump as my toilet is electric with macertor installed so whale pump pumps via y valve to sea cock
I have 2 toilets so lead two feeds into waste tank one pump out to sea cock, but I also have a ball valve at main hose out to y valve to stop any feedback of water to tank unless I'm emptying, this might not be needed depending on your set up
so your set up look good you will just need to pump back to seacock check out the whale gulper toilet waste pump I have one and there pretty good

 

[duncan99210]

Layout 2 is what I’ve installed on our boat. The head pump moves the waste either to the tank or directly to the sea cock. I don’t have a macerator pump, just a simple diaphragm pump to empty the holding tank. It’s now ten years old and I’m aiming to replace it all with a similar set up next year as the pipes have begun to emit odour, as has the tank. I will probably be replacing the tank with a thick walled one from TekTanks and I’m looking at the idea of using petrol pump hosing rather than the white butyl hosing currently doing the job.
Might also look at fitting a macerator pump between head and tank to clear effluent through the pipe work as well as fitting one on the discharge side, again to assist in clearing pipe work of crap. Two reasons for doing that: reducing the formation of scale and reducing the standing smelly stuff to postpone the odour problems.

 

[Tranona]

Two comments.

First you have to decide if you want all your waste to go through the tank or have a direct to sea outlet. If the latter you need to introduce either 2 Y valves or one Y valve and two outlet sea cocks. There are arguments for and against both arrangements. Most macerators have 1" outlets which suggests a dedicated seacock rather than using the main 1 1/2" seacock.

Second with a below waterline tank avoid outlets at the bottom by having a top outlet using a dip tube. Also use a dip tube for the pumpout rather than the external pipe shown in your layouts. Locate your inspection/cleaning hatch so that you can access the end of the dip tubes easily. It is better to have the inlet into the tank on the top rather than the side as it allows you to use the whole capacity of the tank without it flowing back.

Finally keep all runs as short as possible and avoid level runs and particularly dips.

 

[moomba]

Oops forgot to mention as Above T, has stated I have a Y valve with handle to disperse waste to seacock directly or to waste tank
with both toilets , also don;t get sucked into the marine Y valves and ball valves I looked at spa and out door swimming pool ones and they were very robust and good German quality and low and behold cheaper

 

[prv]

Unfortunately my holding tank will be below the waterline.

Aren't you building your own boat? Surely there's a golden opportunity at the design stage to put in a nice tall gravity tank with a straight-down exit directly below a deck fitting - half the benefit of doing it yourself is getting to do these things right instead of being stuck with a production yard's compromises and cost-cutting.

Pete

 

[ashtead]

Holding tanks seem to be a pain in the a***.? Seem to be designed on production boats to block a the drop of a hat . Does a vacuum system not have advantages though? On a normal system the waste just seems to travel through the tank on its journey out and then blockages arise in the tank prior to departure so it's the tank design which fails on what in a direct pipe out would never have an issue?

 

[Tranona]

Holding tanks seem to be a pain in the a***.? Seem to be designed on production boats to block a the drop of a hat . Does a vacuum system not have advantages though? On a normal system the waste just seems to travel through the tank on its journey out and then blockages arise in the tank prior to departure so it's the tank design which fails on what in a direct pipe out would never have an issue?

The downsides of a pumped system are twofold. First they usually result in longer pipe runs because the tank is remote from the loo plus more connections and valves. Second they rely (usually) on an electric macerator to empty the tank, although sensible people fit a diaphragm pump such as a Gusher. If you want to see a bad example of such an installation have a look at some of the older Bavaria systems with the tank on the opposite side of the boat from the loo with over 3m of sewage filled pipe running under the cabin sole!

The problem with retrofitting is that there is rarely enough room in the loo compartments to fit a decent size gravity tank, but as Pete says with a new home build like the OP this should be a priority and easily arranged.

 

[RupertW]

I’d echo the support for designing in a good sized gravity tank as a priority. Our two in a production boat will last quite a few people days (8-10?) and could not be simpler as all the waste goes through one pipe to tank and out the bottom to the seacock - no blocks in 8 years.

 

[coopec]

Thanks for that PVD That website: looks very, very interesting. I'll sit down and study that carefully.
Thanks

 

[coopec]

Thanks for that Tranona.

Here is my holding tank (one at the front)



You can see the markings where I intend cutting an access hole. The "lid" will be 10mm nylon sheet tap screwed/sikaflex 291 to the tank.

It would be a job to get the lid off but I would not expect to do it often

Clive

 

[Tranona]

Sorry to say, Clive that is not a good design for a holding tank. I appreciate why it has to be that shape to locate it under the floor, but tanks are much better tall and square.

However your access is in the right place and suggest you put the two dip tubes for the pump out and macerator pick up alongside so they are at the lowest point. Expect to need to inspect and clean that area fairly frequently if you use the tank a lot!. The inlet from the toilet could be on the top face at the far left or right where it will discharge onto the slope.

If you are at a stage where you can still design in a gravity tank would urge you to consider it.

 

[coopec]

Pete

Aren't you building your own boat? Surely there's a golden opportunity at the design stage to put in a nice tall gravity tank with a straight-do.....

I am building my own boat but to a Bruce Roberts design so I suppose I am retro-fitting it?

Clive

 

[coopec]

Tranona

If I had room I would have made the tank differently but it is a compromise.

To get rid of the stench and crap build-up in pipes and tank would it be wise to flush the system thoroughly with sea water every so often?

Should I use toilet paper especially designed for marine toilets that dissolves very quickly in water?

Clive

 

[Tranona]

Use proper butyl sanitation hose not the cheap plastic type as that is usually porous. Most smells come from hoses. Personally I have never had problems with toilet paper because if you have a Jabsco type toilet it does a good job of breaking everything up before it gets to the tank - even better if you have a macerator type electric toilet. Emptying frequently is good if you can as is introducing fresh water either through the pumpout or for some of the flushing. Using good size dip tubes is important so that it is possible to deal with solids.

 

[BabaYaga]

Sorry to say, Clive that is not a good design for a holding tank. I appreciate why it has to be that shape to locate it under the floor, but tanks are much better tall and square.

However your access is in the right place and suggest you put the two dip tubes for the pump out and macerator pick up alongside so they are at the lowest point. Expect to need to inspect and clean that area fairly frequently if you use the tank a lot!. The inlet from the toilet could be on the top face at the far left or right where it will discharge onto the slope.

If you are at a stage where you can still design in a gravity tank would urge you to consider it.

Just to give a contrasting opinion, I see no big problems with the shape of that tank.
Also, I would not recommend dip tubes (which will make it very hard to completely evacuate the tank).
My advise is to locate the exit tube, or rather valve and tube, at the lowest point of side wall. Pump out tube to deck can be taken from a T-fitting between tank and discharge pump.
The inlet tube and vent tube should also be placed centrally, on the side or top panel, to minimize the risk of these filling when to boat heels.
I can also assure you that a holding tank at or below the water line can work really fine.
It seems to me that most people complaining about blockages have gravity tanks. Whether this is because these are more common nowadays or because they are more prone to block, I am not sure...