SailNet Community banner

1 - 8 of 8 Posts

·
Registered
Joined
·
1 Posts
Discussion Starter · #1 ·
We are a club with a recently purchased 2000 Catalina 34 MK II, previously owned by a husband and wife. The 12-gallon holding tank is being replaced with a 30 gallon tank, more suitable for club operations. Repositioning the macerator pump in the limited space available is problematic. We see on bulletin boards that others have had trouble with infrequently used pumps that are below the water line and constantly subjected to trapped seawater exposure on the through hull end and black water exposure on the pump inlet end. We are considering eliminating the pump and over board discharge capability. This would limit the boat to marina pump outs which is our usual operation in any event. We think the minor inconvenience of not being able to pump out when outside the 3 mile limit is something we can live with. Close offshore operation occurs less than once annually. Is there any safety or practical reason why we should not eliminate the macerator and overboard discharge capability?
 

·
Administrator
Joined
·
7,613 Posts
Depends on your environmental laws in whatever country / state you are in.

Theres no 'need' for a macerator unless theres some legal requirement.

So... what country are you in? And if its the USA, what State? (as some State laws differ)
 

·
Learning the HARD way...
Joined
·
7,495 Posts
There is no legal requirement in the US to have an overboard discharge system. You can remove the macerator and seal the through hull, but this may adversely affect the value of the boat if you ever plan to sell it.

One boat in the club to which I used to belong had a diaphragm pump which was used to pump out the holding tank, but no macerator.
 

·
Administrator
Joined
·
7,613 Posts
There is no legal requirement in the US to have an overboard discharge system.
:) I meant the other way around :)

Some places done like overboard discharge at all.
 

·
Registered
Joined
·
3,159 Posts
A macerator actually qualifies as fist stage sewage treatment.

In terms of pump locations, on my old boat I installed the pump on the top of the locker beside the tank. That way the pump never sat with standing sewage inside it. The impeller design was such that it had no problem priming itself when run.

My current boat has no macerator pump, it simply has a large diameter through hull just below the tank, so you just open the valve and let gravity do the work.

Sent from my SM-G981W using Tapatalk
 

·
Registered
Joined
·
2,232 Posts
We have Lacac toilets. I have gotten rid of macerator pumps and valved the Lavac pump to do both functions.

Elsewhere there was a recent thread in the need of a macerator. IIRC Peggie Hall opined, and others agreed, that any pump will do, a macerator is not required. That is my personal experience, a Henderson diaphragm pump sufficiently “macerates” the effluent, especially if it has been sitting in a tank for a few days.

So that is another option. Use a Lavac and plumb it so only one pump is required. Lavac’s seem to be recognized as the most trouble free and easiest to maintain system. I know we have had very few problems on ours.
 

·
Registered
Joined
·
23,864 Posts
The simplest holding tank set up is having it high enough that it will gravity drain overboard, when desired. Laws often require the discharge handle to be semi-permanently disabled underway. In the US that means tie wrapping it in the closed position or removing the handle, until legally in use. We've installed a keyed switch to activate the mascertor pump. It both helps comply, but it also fully eliminates any crew from accidentally pressing the original switch, while looking for a light switch.

As for seawater sitting in the pump, there really should be a vented loop that the pump pushes the waste up to, so seawater should never siphon back. However, that also means that some amount of waste remains and will permeate at some point down the road. The mascerator pumps are self priming, so they do seem to get most of it out.

The other engineering issue is whether the tank drains from the bottom or through a pickup tube at top. If the bottom, it will gravity drain to the pump, at all times. I strongly prefer a pickup tube, from the top, for two reasons. First, it doesn't gravity drain to the pump on your first flush. Second, a potential leak at the pump doesn't risk emptying the entire holding tank into the bilge.
 

·
Registered
Joined
·
2,232 Posts
Minn,

I agree with your reasoning. Yet our small boat has a bottom drain. I try to not use the holding tank and then pump it clean when I do. I once had a full tank fail massively. NOT FUN. My then 16 yo daughter was not impressed.
 
1 - 8 of 8 Posts
Top