Holding Tanks - Gravity vs Macerator Pump

[nickansc]

We're currently refitting our boat and want to put in a holding tank, clearly a gravity system is great if you can get the tank above the waterline ... however, if you can't ... how good are macerator pumps at getting the waste out? how reliable are they? what should we bear in mind?

the consequences of getting this wrong don't bear thinking about so please help!

Cheers

Nick
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Dream like you'll live for ever ... live like you'll die tomorrow ...

 

[Talulah]

We're currently refitting our boat and want to put in a holding tank, clearly a gravity system is great if you can get the tank above the waterline ... however, if you can't ... how good are macerator pumps at getting the waste out? how reliable are they? what should we bear in mind?

the consequences of getting this wrong don't bear thinking about so please help!

Our holding tank is in the bowels of the cockpit locker.
The boat came with a manual diaphram pump to discharge the waste.
It was a pain in the neck due to the number of people using the boat and the volume involved.
Next I fitted an electric macerator pump.
Lots of arguments about who blocked the pump.
The macerator couldn't cope with sanitary towels or the more expensive toilet paper.
Two seasons later I fitted an electric diaphram pump. Much better. No problems for the next couple of seasons.
Now I'm getting problems. The holding tank is no longer new and sometimes it's possible to get something small (i.e. piece of broken off salt cake) stuck in the beak valves of the pump. If the boat isn't used for a week the valve dry out and the little deposit stops the valve from priming efficiently. The consequence is a trip into the cockpit locker to clean out the valve either side of the pump.
So I'm now literally in process of fitting a manual diaphram pump in-line with the electric diaphram pump to help prime the electric pump when it can't do it itself.
Hope this answers your question.

 

[MoodySabre]

The macerator couldn't cope with sanitary towels or the more expensive toilet paper.

Who hasn't trained their crew properly then both in relation to STs and loo paper purchases?

My macerator has worked fine for two years.I always pump plenty of water in before emptying.

 

[Talulah]

Who hasn't trained their crew properly then both in relation to STs and loo paper purchases?

My macerator has worked fine for two years.I always pump plenty of water in before emptying.

You can put signs up, you can provide nappy sacks, you can talk about it but once you hand the boat over it's out of control. (You must remember there are a lot of third parties on our boat.)

 

[macd]

You can put signs up, you can provide nappy sacks, you can talk about it but once you hand the boat over it's out of control. (You must remember there are a lot of third parties on our boat.)

Tell 'em if the loo get's blocked, you fail the lot of 'em. You could always sweeten the pill by offering a Loomaster Certificate, as well.

 

[RupertW]

Gravity

I prefer gravity but ours are above the waterline, taking up what would be locker space. There was a manual pump out system some years before we bought the boat, as I found when I was trying to remove the smell from one of the heads and found years old **** blocking unconnected pump and pipes.

Diaphragm has got to be best if you need a pump and I'm afraid we have lined bins for all paper and everything else. Always allowed paper before we had a boat with holding tanks but once you've spent a few hours in and out of the water clearing a clogged mess at sea the idea of a loo paper bin doesn't seem so unpleasant.

 

[Networks]

Our boat has a holding tank as supplied by the manufacturer above the waterline and was gravity drained. Every couple of months the tank became blocked and eventually I re-plumbed the system with a macerator pump to drain the tank and valve to bypass the holding tank altogether if required. This has solved the problem, I have had no problems with the system over the last couple of years.
In my opinion the reason the holding tank was blocking was due to a right angle bend at the drain of the holding tank, possibly with a slow bend it would not have been a problem. However it was not possible due to limited space to fit a slow bend.
So my advise would be, if you fit a gravity system, make sure you have very short pipe runs and no tight bends. I am glad I fitted the macerator and would do the same again.

Kevin

 

[prv]

Our boat has a holding tank as supplied by the manufacturer above the waterline and was gravity drained. Every couple of months the tank became blocked
[...]
In my opinion the reason the holding tank was blocking was due to a right angle bend at the drain of the holding tank

Ouch!

I would always prefer a gravity tank if possible, but it should be vertically above a ball-valve seacock so that the pipe is a dead-straight line from tank to sea. With an appropriately-positioned inspection hatch (preferably not in an accommodation space) you would then be able to rod vertically down right through the whole system and clear any blockage short of concrete. Note the retention valve should be at the tank rather than using the seacock, otherwise the pipe acts as a mould and settling space for a plug of paper and other solids.

Pete

 

[r_h]

Always allowed paper before we had a boat with holding tanks but once you've spent a few hours in and out of the water clearing a clogged mess at sea the idea of a loo paper bin doesn't seem so unpleasant.

+1

and with the boat in Greece even guests aren't surprised, as that's what they have ashore in any case.

The tank is a above the waterline, but with a manual diaphragm pump that helps to empty it if necessary. Only problems have been with limescale narrowing the pipes - I now intend to replace them every 5/6 years, whether they need it or not

 

[RichardTaylor]

Slightly Off Topic: Our new boat has a gravity holding tank, what is the score with breaking up solids (does this get done by the loo on pump out of the bowl?) and also loo paper - is there any paper which is soft like Andrex but dissolves/breaks up readily?

 

[MoodySabre]

Slightly Off Topic: Our new boat has a gravity holding tank, what is the score with breaking up solids (does this get done by the loo on pump out of the bowl?) and also loo paper - is there any paper which is soft like Andrex but dissolves/breaks up readily?

The pump does a good job, err what I meant say was.......

Tesco Value but go gently

 

[rotrax]

Slightly Off Topic: Our new boat has a gravity holding tank, what is the score with breaking up solids (does this get done by the loo on pump out of the bowl?) and also loo paper - is there any paper which is soft like Andrex but dissolves/breaks up readily?

Hi, We have a factory fitted holding tank and macerator pump.The tank is in the bowels of the boat,and has overboard and shore side outlets. No problems in the 30 months we have had her. We use Tesco Value loo paper. It appears to be about the same specification as the expensive ones sold by chandlers and is a fraction of the price.

 

[Jamesuk]

Who hasn't trained their crew properly then both in relation to STs and loo paper purchases?

My macerator has worked fine for two years.I always pump plenty of water in before emptying.

I totally agree looks like someone cannot control there crew. Maybe a "master chief" is involved.

As for the pumps we use a Jabsco "quiet flush" macerator pump connected to a gravity tank above the waterline. Stored in the cupboard so clearly lost space there but better be smell free than clogged up.

As for the pump it is so simple to take apart it is a total joy in terms of ease that is. Although I was just servicing it so no smelly water for me.

 

[Bosun Higgs]

Occasionally you do a project on the boat that really works well - as opposed to those that you end up re-doing. My holding tank was a goodie that functioned for 7 years till I sold the boat without a single problem.

The tank was stainless and when it was made I had the drain pipe through the top of the tank and down to about half an inch above the bottom. The tank itself was above the waterline so I could fit a diaphragm pump to the drain pipe and then directly to a sea cock. The pump was just used to start the syphon and the tank emptied itself. No diverter valves to get blocked just the pump and a sea cock.

The feed into the tank was from a normal Par ITT type loo. The piping was solvent welded abs from B&Q since that sort of pipe doesnt get to stink like the flexible eventually does. Again no diverter valve - everything that went into the loo went through the holding tank.

Policy was that toilet paper etc got put into a pedal bin by the loo - flotilla style. Some people didnt like that idea but it worked and never smelled.

 

[nickansc]

thanks everyone, not the most exciting of topics so greatly appreciate all your time