Holding tank discharge pump question

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The overboard discharge pump from the holding tank on my boat had to be replaced last year. The company that did the work couldn't find an exact replacement and supplied a pump made by a company called Gianneschi and Rammacciotti, a company that I have never heard of. Unfortunately, the ham fisted animals that actually did the work managed to spill some effluent in the bilges whilst changing the pump and didn't bother to clear it up afterwards. I didn't find out until I went to the boat some weeks later by which time the bilges were ponging like a sewage works. I have cleaned and disinfected the bilges thoroughly but there is still a smell from around the new pump which I can't get rid of
My question is this - are holding tank discharge pumps just standard centrifugal pumps or are they special pumps made from specific materials designed for handling sewage effluent? There doesn't seem to be any leak from the pump so why should it be smelling?
 
Mike,
You sure its the pump thats smelling and not the vent?

Think these pumps should have a macerator gizmo inside also!

Had an awful problem on a previous boat that had a rotten egg pong coming from the vent, and nothing I tried could 100% cure it.

Rob.
 
Typically the pump motor is fairly standard, but it will have a macerator blade in front of the impellor.

Like this one HERE.

(had to change it last season: ended up with feet in black water /forums/images/graemlins/mad.gif Quite easy to end up having a spillage. No excuse for not cleaning up afterwards, though.)
 
They are very rarely centrifugal pumps. Most are diaphragm (like the Sealand ones) or are jabsco type pumps with a macerator blade added (eg the Johnson black tank pumps). Both these types will prime dry to a couple of meters head, whereas centrifugals are often not good primers.

Anyway, back to you question on materials, I don't know. The body of the Johnson type is small so even if it wasn't smell-resistant plastic the odour would be small. The diaphragm jobs are much bigger and you'd expect them to made from pong-free plastic but I'm not actually sure. It would be good to know if your pump is diaphragm type - if it is, there will be a large surface area inside smeared with shoite. If the pump's plastic material is letting that through then that is you smell source, and you need to swap it for a proper shoite pump eg the sealand T series (which is vv good, been going for years, highly recommended by headmistress, millions installed). I have/have had both Johnson and Sealand and neither smells.

Alternative is that the smell isn't seeping thru the plastic, and perhaps the pump just needs a serious scrub/clean with bleach or bilge cleaner type stuff? If the animals had shoite on their hands and assembled it all that way the pump body/casing will pong?
 
Rob, the vent exits from the other side of the tank and it's definitely clear because I removed the pipe and pumped air threw it. I thought it was a blocked vent myself but it isn't
 
Actually I've just found it on the net HERE (page 8 model ECO MV44) and I was wrong. It's not a centrifugal pump but a single screw pump and according to the data, it's constructed of bronze and suitable for waste pumping so the pump itself doesn't seem to be the problem. Could be that you're right and it needs an even more thorough clean with something a bit stronger. I used a disinfectant type bilge cleaner. Maybe a strong bleach would be better
 
Blimey, that's a lovely pump, superyacht stuff, way better than anything on a production brit boat. The smell is certianly not coming from the pump!
 
The vent has a filter in line, or at least mine does, activated charcoal or such like. It's normally quite a big filter, as I think the idea is that the amount of air displaced by each flush is stored in the filter, so the charcoal has time to work on the smell between flushes.

If the filter has expired, or somehow been soaked in the brown stuff, then you'd get toilet smells outside the boat, but i'm guessing yours are inside, if you suspected the pump?
 
Yup, I have got a filter on the vent pipe and every flush does cause a bit of whiffy air to exit the boat but the smell is definitely on the inside and definitely around the discharge pump. I think jfm is right and I should concentrate on cleaning the pump body
 
Thanks, Firefly625. Yes, you're right that non sewage standard pipe can become porous but I had all of mine changed at the same time as the pump was changed
 
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Blimey, that's a lovely pump, superyacht stuff, way better than anything on a production brit boat. The smell is certianly not coming from the pump!


[/ QUOTE ]

OK, that makes me feel better about the cost of it. Any idea whether these pumps can be damaged by dry running?
 
I used to suffer from a pongy vent pipe but for the last couple of years I always pore some tank pong remover down the loo before we leave. No more pong.

UNI_054850_l.jpg
 
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[OK, that makes me feel better about the cost of it. Any idea whether these pumps can be damaged by dry running?

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Let me guess: €450 just for the pump?

Those pumps are the biz. Most types can be run dry indefinitely. Here are the rules for shoite pumps:

1. Macerator/jabsco type, as linked to above: destroyed if run dry even for 30seconds, but can be run indefinitely agianst a blockage or a closed seacock. Prone to blocking
2. Diaphragm type, like Sealand T series: can be run dry indefinitely. If run agianst a block or closed seacock the jokers invert and you need to strip down to get it working again, but no damage done. Rarely block - can even pump large unmacerated, er, solids.
3. Screw pumps. Rolls Royce. Normally can run dry indefinitely but the ones with idelr rotating screws rely on the pumped fluid for lube. Still, they will run fine for quite a whie dry, not like the macerators that just die in less than 30secs. Could damage if run agianst closed seacock, and such good pumps that they might split a pipe or joint. Better to fit exactly the right circuit breaker so that if it tries to pump agianst a blockage or shut seacock it'll just overcurrent and trip the breaker. Can pump fairly chunky solids - depends on screw size
 
Princess fitted two seperate systems on the 67.

The main one is a diaphram pump and the backup system uses a macerator.

I'm dont paarticularly like the system - the backup is OK - not really used it but the main is on an automatic system. If you leave the seacock open and switch it to auto, it will automatically discharge when the tank gets about two thirds full. I like to keep the seacocks closed so I, effectively, use the system manually.

I seem to remember that you had an auto seacock (or something) fitted to your old boat - probably something I should do - at the moment, I have to lift carpets etc just to open the seacock every time I want to empty the tanks.
 
Thanks jfm, very useful. Cost of pump and fitting was about €700. Good news about running the screw pump dry because I often do as I have no tank empty indicator
 
Is it the Sealand auto system, with the key switch? If yes, then I'd suggest keep it and add the elect seacock/relay that I recently installed. Easy job, cos the elec seacock just screws into your existing manual seaccok, then you re-attach the flex hose. 5 core wire needed from switch panel to elect seacock

Electrically I set it up as follows (pic below). Left switch is power to the system. Next switch (latching) is open/shut the seacock. Third switch (non latching) is manual operation of the pump. Since the pic, switch rockers have been labelled in white print. Also, this isn't the prettiest switch panel but it is hidden by pressing a button on the dash that makes a cream lid slide up electrically. The switches are Carling and on the p67 you'd use the other series of Contura rockers, to match your dashboard. The rockers I have used are the ones that match the Sq58

IMG_2937.jpg


To dump the tank I also use it in effect manually, as you do, but the procedure is as follows:

1. Open seacock with 2nd switch. Takes 20seconds
2. Operate the "auto" keyswitch. This runs pump till green "empty" light comes on". Go and make a cuppa tea while this is happening!
3. Operate 3rd switch to pump a bit more out, to really empty the tank
4. Shut seacock using 2nd switch. Check that "shut" light comes on.
5. Turn off the "auto" keyswitch if pedantic, though it's not necessary cos of the relay mentioned below

The seacock open/shut indicator lights are fed by microswitches within the seacock unit, so they're a reliable indication. I've put into the discharge pump wiring a relay that interrupts its 24DV supply, and that relay is normally open but is closed by the wire that illuminates the "seacock open" light. So it is impossible for an operator incorrectly to try to run the discharge pump agianst a shut seacock. And if you press the seacock shut switch it instantly isolates the pump, quite niftily. So, in practice, i leave the key switch at the "auto" position yet I know the pump wont discharge till I flick the "seacock open" switch, so I retain manual control of when the tank dumps.

I have a back up but it consists of a whole new pump carried as spare. I dont want a permanently plumbed/installed back up! That would mean too many pipes with old shoite inside them, imho - no thanks!
 
Yes - I remembered that you had something like this.

Difficult to say if the system is a Sealand or not - the panel is built into my DC panel but has 4 lights ranging from green (empty) through amber to red (full). There's a three position rocker switch - middle position is off - left (latch) is auto - and right (spring momentary) is manual. So to operate manually, you have to hold your finger on the switch. If the tank is full enough though you can switch to auto.

There is also a microswitch fitted to the seacock itself and the pump wont run unless the cock is open.

So, as you say, it should be quite easy to install one of these automatic seacocks - I wouldnt even need to wire back to the panel - just install above the floor to (in a cupboard or something) so that I dont have to keep lifting the ruddy floor panel - which is a bloody pain because it involves lifting carpets etc.

And as you say, I could also use the existing seacock microswitch wiring to interlock the pump so that it couldnt be operated against a closed seacock.

So, where do I get the automatic seacock from? - are there different sizes?

Seems like a job for the winter - good excuse to go down to the boat after the season finishes.
 
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