Chances of diaphragm pump not strong enough to pump black water to 0.5m below WL?

[vas]

odd Q, will be sure about that on Sat afternoon once MiToS is back on the water.

So, have a massive 1.5inch Rheinstrom diaphragm pump for my 100lt blackwater tank. Cannot for the life of me find the model # but it;'s a 24V 700euro pump, so a substantial bit of kit.
Tank is all below w/l sitting on the keel effectively so lowest point is .8m below W/L and top probably .5m below W/L
Rheinstrom is placed slightly (say 5cm...) above the top of the blackwater tank.
Exit is via a 1.25inch trudesign thruhull (and matching seacock) by the keel, so again .8m below W/L

After all this intro, the facts:

Tried emptying the blackwater tank (was messing about with the never complete wiring to the pump) and I have an unconfirmed feeling that it wasn't emptying.
Now on the hard run the pump for a few secs and surely enough sh1t came out (onto a bucket strategically placed underneath...)
So pump and the two duckbill valves work.

Are there any chances that this big bugger diaphragm pump is not strong enough to overcome the static of the .8m and cannot empty the tank by pressing the sh1t down the pipe?
I can re-pipe it to an injection above waterline, but wouldn't like to mess with sh1t anymore atm.

Any ideas welcomed!

cheers

V.

 

[jfm]

odd Q, will be sure about that on Sat afternoon once MiToS is back on the water.

So, have a massive 1.5inch Rheinstrom diaphragm pump for my 100lt blackwater tank. Cannot for the life of me find the model # but it;'s a 24V 700euro pump, so a substantial bit of kit.
Tank is all below w/l sitting on the keel effectively so lowest point is .8m below W/L and top probably .5m below W/L
Rheinstrom is placed slightly (say 5cm...) above the top of the blackwater tank.
Exit is via a 1.25inch trudesign thruhull (and matching seacock) by the keel, so again .8m below W/L

After all this intro, the facts:

Tried emptying the blackwater tank (was messing about with the never complete wiring to the pump) and I have an unconfirmed feeling that it wasn't emptying.
Now on the hard run the pump for a few secs and surely enough sh1t came out (onto a bucket strategically placed underneath...)
So pump and the two duckbill valves work.

Are there any chances that this big bugger diaphragm pump is not strong enough to overcome the static of the .8m and cannot empty the tank by pressing the sh1t down the pipe?
I can re-pipe it to an injection above waterline, but wouldn't like to mess with sh1t anymore atm.

Any ideas welcomed!

cheers
V.

from description of pump it feels big enough to pump against .8m head. Crikey it must be specced much higher than 0.8m otherwise why bother making it!
Are both duckbils in good nick? The more the head the more you need them to seal
To check If it is pumping well, launch with an empty tank then run pump. you will hear it pumping air into the sea- the bubbles will be noisy. If no air is pumped then it can't do a .8m head.

 

[vas]

thanks John,

got a second one that does more than 1m head without any problems. It's highly unlikely it cannot do it, maybe the duckbil valves need testing (nice, they'll be covered in sh1t right now, looking forward to the job )
back in the water tomorrow, will test it at the sea with son at deck instructed to check for colour change in the water

cheers

V.

 

[vas]

closing a thread I started...

On the way back from a long w/e I stopped in the middle of the bay (8nm of water all around) switched engines off, and had the crew look for tell tales of tank emptying.
Oddly enough (probably due to slight current) the light brown stuff with tiny solid bits (I'd rather call them flakes) did appear on the wrong side of the boat. Took it maybe 4mins to start pumping little bubbles, so job done, pump is good enough and the piping and routing is OK. So messy job ticked with no need for interaction with the pipework
Never had experienced this blackwater tank emptying, I was amazed at the lack of more solid and dark substance. Guess the macerators are doing a decent job.

cheers

V.

 

[jfm]

closingI was amazed at the lack of more solid and dark substance. Guess the macerators are doing a decent job.

Yup, and the content is more flushwater than "black". If you have plenty of water and opportunity to empty the tank it's good to double flush so as to keep the black cocktail even more dilute

 

[vas]

Yup, and the content is more flushwater than "black". If you have plenty of water and opportunity to empty the tank it's good to double flush so as to keep the black cocktail even more dilute

thanks John,
I'll skip that until I fit a N2K gauge on the blackwater tank as currently I have only a faint idea of how much stuff is in there...
Final Q, do you recon seawater flushing is "killing" more of the stuff and creating more neutral liquid to keep on your tank compared to fresh water which I'd expect to be a paradise for germs and all other nice organisms to live and multiply?

Mind, I'm on cheap el. toilets sucking seawater and plain macerators at the bottom of the bowl and not planning to replace them except for the abysmal noise they produce even bolted on 10mm rubber flanges with rubber washers on each bolt on each hole. I wonder how much noisier would they be without all that effort!
I mean I wouldn't dare flush in the morning with all kids sleeping around in the quiet anchorages we were last two nights...

cheers

V.

 

[jfm]

Once inside the tank I don't know whether seawater or freshwater makes a more hostile environment for the stuff you don't want to thrive. I'm confident though that freshwater isn't a problem on that score. All round I think freshwater flush is way better on the smell front, because of the well known problem of smelly seawater sitting in pipes and toilet bowls etc