Holding tank pump

SolentSnowgoose

SolentSnowgoose

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I need to fit a holding tank and have looked at a whole range of layouts and system designs.
I had hoped to avoid using a pump to empty the tank but space is limited and a gravity discharge means a longer inlet and hence more flush water to clear the pipe which will rapidly fill a 50L tank.
Hence I am going to have to use a pump ... with all the attendant horrors of blockages..
It seems there are two basic designs ... Gulper diaphragm pumps and macerator impeller pumps.
Any advice or experience on which is best appreciated
My current leaning is towards a macerator pump in the vain hope that it will chew stuff up rather than getting blocked.
I fear the wrong choice could leave me in the .....
 
If you have a Lavac, all you need is two diverter valves to serve the holding tank. The Lavac pump 'naturally' macerates the contents and either operates overboard, into the tank or exiting the tank. Simples.
 
SolentSnowgoose said:
Any advice or experience on which is best appreciated
My current leaning is towards a macerator pump in the vain hope that it will chew stuff up rather than getting blocked.
I fear the wrong choice could leave me in the .....
Click to expand...

I have had a holding tank under the fore peak bunks, emptied by a hand operated diaphragm pump, for 35 years and never had a blockage. In fact I believe that such a system has many advantages over a gravity tank, but I know that many disagree on this.
My pump is a Whale Gusher 8 (no longer manufactured I think). I have changed the rubber parts once or twice, also at one time a metal part (possibly a bolt, don't quite remember) inside the pump snapped because of severe corrosion.
I see that Whale now has a special hand pump for black water - when I replace I will go for one of these.

Edit: In case you wonder about the time and effort, for me to empty a full tank of circa 50 litres takes about 110 strokes on the pump in as many seconds. Certainly not hard work.
 
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Congratulations ...you are installing the most sensible option.......what gets pumped into the tank through the top gets pumped out through the top......using a Whale Henderson MK5 Waste Pump....(my choice)(ASAP will supply one).. Relying on a gravity arrangement to empty the tank will work fine.......until either the outlet blocks...or the tube/valve needs replacing...and then someone (you) will have all the fun of grovelling around underneath the tank to do it.
Also....if you mount your tank so that it is not `horizontal`...then at anchor you will have less potential for noise from small amounts of content `slopping around`..... This arrangement has worked well for me over 15 years.
 
tillergirl said:
If you have a Lavac, all you need is two diverter valves to serve the holding tank. The Lavac pump 'naturally' macerates the contents and either operates overboard, into the tank or exiting the tank. Simples.
Click to expand...

This is what i have. Diverter at the pump inlet to suck from the toilet or the tank, one at the outlet to discharge to sea or tank.

Without a Lavac i would use a diaphragm pump too. Whale or Jabsco both make a suitable pump and with a diaphragm pump it's possible to fit manual and electric pumps inline, should one desire. I have had macerator pumps too and they will wake the dead and are easier to block than diaphragm pumps.
 
My boat uses one of the macerator pumps to empty the tank. It’s OK, but mixing electricity, water and poo does not a reliable pump make.

Interestingly, you have to keep using the thing to stop it sticking. The instructions that come with the replacement Jabsco pump do give instructions on how to get it turning again when it sticks! The Jabsco macerator pumps are around the £200 mark, although you can get cheaper. One of the first things I had to do with my boat was change the pump. Thank goodness that the pump end of the tank can lift clear of the hull moulding allowing replacement of the pump without removal of the tank.

Given the choice I’d remove it completely (this makes no-one popular…) or install a gravity fed holding tank.
 
tillergirl;6193069]If you have a Lavac, all you need is two diverter valves to serve the holding tank. The Lavac pump 'naturally' macerates the contents and either operates overboard, into the tank or exiting the tank. Simples.

PaulRainbow said:
This is what i have. Diverter at the pump inlet to suck from the toilet or the tank, one at the outlet to discharge to sea or tank.

Without a Lavac i would use a diaphragm pump too. Whale or Jabsco both make a suitable pump and with a diaphragm pump it's possible to fit manual and electric pumps inline, should one desire. I have had macerator pumps too and they will wake the dead and are easier to block than diaphragm pumps.
Click to expand...

Please could you elaborate on the system you are using. I have a lavac manual toilet but I just cannot envisage exactly the plumbing method you and tiller girl are using to enable the Henderson pump to perform the separate actions of pumping the toilet and emptying the holding tank. A diagram however crude would be appreciated. Failing that any explanation that a 5yr old would understand may trigger my epiphany moment.
 
Besonders said:
Please could you elaborate on the system you are using. I have a lavac manual toilet but I just cannot envisage exactly the plumbing method you and tiller girl are using to enable the Henderson pump to perform the separate actions of pumping the toilet and emptying the holding tank. A diagram however crude would be appreciated. Failing that any explanation that a 5yr old would understand may trigger my epiphany moment.
Click to expand...

The pump inlet goes to a Y diverter, which connects to the toilet and the holding tank outlet. Depending on the position of the diverter valve the pump will suck from the toilet or the tank.

The pump outlet also goes to a Y diverter valve. This connects to the tank inlet and the seacock. This allows the pump to discharge into the tank, or straight to sea.
 
Besonders said:
tillergirl;6193069]If you have a Lavac, all you need is two diverter valves to serve the holding tank. The Lavac pump 'naturally' macerates the contents and either operates overboard, into the tank or exiting the tank. Simples.



Please could you elaborate on the system you are using. I have a lavac manual toilet but I just cannot envisage exactly the plumbing method you and tiller girl are using to enable the Henderson pump to perform the separate actions of pumping the toilet and emptying the holding tank. A diagram however crude would be appreciated. Failing that any explanation that a 5yr old would understand may trigger my epiphany moment.
Click to expand...

If you pm me an email I can attach a plan. Cancel that - found the photo. The water 'in' was not installed at the time of the photo with arrows

Holding Tank Drawing 1 by Roger Gaspar, on Flickr

P1010258 - Copy by Roger Gaspar, on Flickr

P1010250 - Copy by Roger Gaspar, on Flickr
 
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