what pump for black water tank discharge?

vas

vas

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slightly lost here,

went to 3 different shops looking for a complete black water tank solution around 100lt

all three suggested polyethylene tanks (which as far as I understand is the right material)
but in terms of pumps there were 3 different solutions :rolleyes:

one suggested a low exit to a macerator pump gravity fed. Don't like it, wont have it!

second suggested a top exit (with a pipe going in the tank of course) with a suction pump (rather expensive these pumps at 360euro for a vicking or 180 for a tmc!)

third one suggested again a top exit but with a macerator pump! Tried to explain that from whatI understand macerator pumps at 1.5inch wont really suck **** 40cm up but he insisted that the system works.

Needless to say that third option is much cheaper tha second (ok, not even considering the first!) so what do I do?
what does the panel recommend?
Pump will be secured on top of the tank, tank height around 30-34cm

cheers

V.
 
Piers said:
Hi vos. Our Fleming uses a 24v DC Sealand T pump (T24VDC) and in 10 years it's never failed. (http://www.leesan.com/index.asp?m=3&b_idno=12&p=105&t=Sealand T Series Discharge Pump, 24v DC)

The guys at Leesan are really helpful - give them a call and see what they recommend.
Click to expand...

thanks Piers,

so what you have is a type 2 solution, with a diaphragm pump. Yours is at the 360GBP mark, a similar and obviously lesser one by whale would be at 250 and I'm trying to keep the cost of the whole assembly at under 500euro. Which is becoming tricky I suppose :(

cheers

V.
 
Vas, Rafiki has a set up similar to your 2nd scenario. The mercerator hose goes in to the top of the black tank, and discharges through a seacock in the hull.
 
Raf,

so that means that a plain macerator pump with a twin impeler (brass to chop things up and rubber for creating the necessary vacum I guess) is sufficient!
Then I can get a Matromarine 78lt kit with sender, gauge, diverter valve etc for 290euro!

cheers

V.

PS. will call the guy tomorrow and will let you know
 
vas said:
thanks Piers,

so what you have is a type 2 solution, with a diaphragm pump. Yours is at the 360GBP mark, a similar and obviously lesser one by whale would be at 250 and I'm trying to keep the cost of the whole assembly at under 500euro. Which is becoming tricky I suppose :(

cheers

V.
Click to expand...

I bought from Environmental Marine (USA) for £180. I also bought a number of other items so cannot break down the carriage charge.
 
vas said:
one suggested a low exit to a macerator pump gravity fed. Don't like it, wont have it!
Click to expand...
Actually, there's nothing so awfully wrong with that, if done properly.
When I replaced the WCs with Tecmas, I also fitted a black water tank.
And since the pump fitted inside the WCs was supposedly good also for discharging the tank, I fitted one of them at the tank bottom.
Which means that in case of failure of one of the WC pumps, I can use it as a replacement (though only bypassing the tank and discharging directly, of course).
Result: 11 flawless years (and counting, touch wood...) :)
 
MapisM said:
Result: 11 flawless years (and counting, touch wood...) :)
Click to expand...

and I do remember JFM not being exceptionally happy about it ;)

comeon admit it, designing from scratch it's not the best way of doing it, especially as Murphy's law says you'll be touching lots of smelly wood soon :p

sincerely hope not, but I wont be happy with pipes exiting from the bottom of either black or grey water tank. BTW, my 16lt whale grey water tank has bottom exit and I'll remodel that for a top exit next week, watch this space...

cheers

V.
 
ah,

and while we're at it, how much fluid fills the tank on every flush?
OK, approximate values, and assuming we're not having a curry everyevening!
Are we talking 2-3lt a flush? Trying to establish how often a 75lt will fill up in order to decide if it's convenient or should really go for a 100lt one.
I'd be happy with a week for a family of four.

cheers

V.
 
Piers said:
I bought from Environmental Marine (USA) for £180. I also bought a number of other items so cannot break down the carriage charge.
Click to expand...
thanks will check them although tax stings badly on values over 100usd so I'm avoiding them at all cost!

MoodySabre said:
I have number 3 version. Works fine. See Tek tanks website for various layouts. I think their tanks are made from HDPE
Click to expand...
MS and rafiki, do you remember what macerator pump do you have installed on your systems? Twin impeller ones?

MS, yes high density PE is the best it seems, TEK do a nice range of custom tanks, thanks for the pointer!

cheers

V.
 
vas said:
and I do remember JFM not being exceptionally happy about it ;)
Click to expand...
LOL, yeah, but J is never happy with anything which isn't 100% engineeringly kosher.
Not that I disagree with that, but I tend to put some value also on simplicity, particularly on boats... :D
 
IMHO, the black water tank pump is one of those components that you really don't want to have to replace any time soon so buy the very best you can afford. Whatever you buy must be capable of dry running for extended periods without damaging the mechanism and obviously it must be capable of handling solids. I fitted a black water tank system in my boat 3yrs ago and I was recommended to buy one of these
http://www.nonstopyacht.com/static/browse/session/Product/View_/GNR&2DECO&20MV&2044&2D12.htm
It was expensive at the time (around €700 if memory serves) but it's worked without problem so far
 
vas said:
thanks will check them although tax stings badly on values over 100usd so I'm avoiding them at all cost!


MS and rafiki, do you remember what macerator pump do you have installed on your systems? Twin impeller ones?

MS, yes high density PE is the best it seems, TEK do a nice range of custom tanks, thanks for the pointer!

cheers

V.
Click to expand...

Sorry Vas, am too far away to check (Sao Paulo).
 
no specialist on the subject,
but we have just replaced our old SS black water tank, with a new custom made PE. (pictures to come)
all connections are as orriginal,
the oulet was/ is a bottom side exit, (30mm hose) with a self priming pump (Sanguineti)
for the pump, I think many (cheaper) alternatives available.

its the pump here on the bottom left side,
P1110274.jpg
 
I don't like the bottom exit from tank (solution #1) becuase it feels susceptible to leaks so I use a diaphragm pump to suck from top of tank. All that said, MapisM does have a good point and actually a well made bottom joint is so simple it should never fail, so i wouldn't argue with MapisM on this. Plus he gets to use a high quality Tecma impeller pump, which is a nice piece of kit

I use sealand T series diaphragm pumps though i don't love the latest versions. Piers' 11 years of happy use of T series is becuase his is 11 yo before (perhaps) they started getting made in china or wherever. One of mine on Match 1 split the diaphragm and the result was a bit messy especially. So I'm a bit negative on the current T series pump and would like to find something better but have not done the research yet (I have 2 T series on Match 2)

Alas there is no such thing as a cheap 1.5inch diaphragm pump. You're into e500 territory

Overall i prefer your second idea, with a quality pump. The third might work, but as the macerator wears its ability to pull the 400mm head will reduce and thus it will wear more - it needs the pumped fluid for lube so it is a vicious circle really
 
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