Manual holding tank pump out pump - distance from tank

[benzy]

Currently, we have a 50ltr holding tank, above the waterline, which pumps out via a Jabsco macerator pump via a seacock. Pipe run from the tank to the macerator is about 0.5m of 50mm hose. Then from macerator is about 3m of 25mm hose.

The macerator has corroded and is leaking (not very pleasant), and I have read elsewhere that this is common. So, not being afraid of a bit of elbow grease, I'm thinking of replacing this with a manual diaphragm pump (far less chance of corrosion).

However, since it will require good and comfortable access to operate the pump, I am limited for options for where to situate it. Therefore, my preferred option would be to situate the diaphragm pump near the seacock, which will be a roughly 3m pipe distance from the holding tank. This pipe run is roughly horizontal, but does have a slight dip in the middle (yes, I know this is a terrible design - I inherited it and it's on the long term list to change!)

I'm wondering if this will work well in "pulling" the contents from the holding tank given the distance. I know these kinds of pumps will prime just fine when pumping water from the bilge, but the holding tank contents might not be so "fluid".

Any thoughts or advice?
Cheers

[Sailmonkey]

Why not an electric diaphragm pump? It will be just fine for the task you propose.

[jeepbluetj]

If your tank is above the waterline, can you find a way to gravity drain it?

[peghall]

Read the specs for the pump--manual or electric--of your choice. They're in the owners manuals, which you should be able to find on the mfr's website.

[rwidman]

By far the easiest thing to do is replace what you have with the same or a similar pump. I had the long bolts on my pump corrode and the manufacturer sent me replacements in a new style that are not supposed to corrode.

Even if a replacement pump only lasts several years, that would be simpler than re plumbing everything to fit a manual pump.

[Dockhead]

I agree about replacing with the same pump.

The simplicity of a manual pump is appealing at first glance, but . . .

1. What happens when the big diaphragm rips? It doesn't really bear thinking, does it?

2. Are you ok lifting a sole plate to get to the pump, to fit the handle?

3. It's not all that big a job to replace some hoses, but even a couple of extra hours of your time -- is it worth it? Just to replace a reasonably reliable electric pump with a manual pump which will be no more reliable?

4. The manual pumps do not macerate. Maceration is a very good thing -- to prevent clogs in your piping, for one thing, and for the environment, for another.


I have exactly the same setup as you with the same electric Jabsco macerator pump. You can buy the impeller housing separately from the motor (the motor lasts basically forever in this kind of duty). It's not expensive, and changing it out is is 10 minute job. Then you'll be good for another 10 years of service. You'll decide yourself, of course, but that's what I would do.

[SailingFan]

As for the differences in pumps, especially the macerator options, I currently have a brand new in the box Jabsco macerating head, and am installing it to replace whatever was there in my '78 H27. The current incarnation had a discharge through hull, but possibly no holding tank (as I cannot locate a holding tank anyplace on board, and no pumpout location on the deck either). I do see a discharge valve on the hull interior that seems jammed in the closed position (so far), and I also see a vented loop installation with associated hoses in place already. I will of course be removing and replacing those hoses in entirety!

I now have need to get a plastic holding cell as well as a selector for tank or discharge. I found several selector valves, so that is not the hard part. I assume I need to go with the largest hose possible on that valve as well. The problem is that I need to determine the best place for a holding tank, and how large that holding tank should be.

The original versions of my vessel back then had the option for a 13 gallon holding tank, which to me seems a little on the smaller side. I was hoping I could cram a 20 gallon tank someplace (possibly a pipe dream on a 27 foot boat), but also have a desire to keep the hose runs relatively short. If I could keep them within perhaps a few feet of the head, that would be fantastic news.

Another thing is that I need to site the cell so that it is easy to get a suction line installed for it for deck discharge at pump stations. I have a place in mind, and there is already a deck fitting near where I want it, but I think that fitting was installed for use with the water tank on board (aluminum, 35 gallon, and so not so great for sewage). That line is severed just below the fitting, so I am wondering if I can use it for the sewage pumpout instead. Are those fittings the same general size? It looks about right, but does not have the sealing rubber plug in there... I could easily hook it to my storage tank because it is close to where I want the tank to be located.

Also, is there a negative to installing the holding tank under the vee berth, in the space normally used for storage, aft of the water tank? I included a photo of the area directly near the head location, with one of the hoses coming out of a round void beside where the toilet is mounted. There is also a void behind the toilet and above this hole, where I can run hoses and the like.

[SailingFan]

I don't know where that second photo is from, but I THINK it is one of my quarter berths, where I was thinking of putting a fuel cell, fresh water cell (and thereby make room for additional 35 gallon tank for the head in the vee berth in place of the current aluminum fresh water tank, also original to the boat, but the camera is oddly angled for some reason), or making a sliding storage system to store food and such on board, so please disregard that one.

I also have room under two settees I could use for a sewage tank, if needed, but need to decide soon, because I am about to tackle this thing, and need to get space allocation decided. Here is a link to my vessel (to show the relative position to what is already on board...).

HUNTER 27 sailboat specifications and details on sailboatdata.com

To the OP, I agree with the others who say that replacing that aluminum tank rather than converting it to sewer is wise (and will piss off a future owner who will likely try to use that as a negotiation instrument against you). Heck if you coat it, put fresh water in it and keep it for that, or for wash water if nothing else, because using it until urine cuts through seems like something my wife would make me walk the plank for... But that is your decision I suppose. I just would seriously consider the consequences, that's all.

[Terra Nova]

The manual pump should work fine. But it will likely require that you increase the size of the thru-hull fitting, sea cock and discharge hose. The trap in the supply hose run will cause waste to collect and may require the hose to be replaced more frequently.

[benzy]

Thanks for all the replies.

I will replace all the hoses anyway, since they area bit old and stinky.

Overall, it seems best to perhaps just stick with the current setup.

Would installing a sea cock on the holding tank outlet help by stopping the contents of the tank being able to run down and sit in the macerator between pump outs?

[Terra Nova]

Not a sea cock, but you could add a ball valve at the holding tank to prevent waste from sitting in the hose and macerator. Also makes a cleaner job of working on the discharge plumbing.

[Dockhead]

Originally Posted by benzy

Thanks for all the replies.

I will replace all the hoses anyway, since they area bit old and stinky.

Overall, it seems best to perhaps just stick with the current setup.

Would installing a sea cock on the holding tank outlet help by stopping the contents of the tank being able to run down and sit in the macerator between pump outs?

Is the holding tank outlet on the underside of the tank?

On my Moody, the 120 litre holding tank, made by TekTanks, pumps out through the TOP of the tank via a dip tube. If yours is like this, then you won't need any ball valve.

Otherwise, I think a ball valve would be good to have, in order to isolate the piping, but I don't think closing it will prevent effluent from sitting in the macerator. Unless perhaps you rinse out the tank before closing it, but how are you going to do that? I don't think I would worry about it -- the upgraded impeller housing studs seem to do just fine, and everything else is stainless or plastic.

[Terra Nova]

Originally Posted by Dockhead

...Unless perhaps you rinse out the tank before closing it, but how are you going to do that?...

Just flush the head with fresh water or put it in the deck pumpout.

[Dockhead]

Originally Posted by Terra Nova

Just flush the head with fresh water or put it in the deck pumpout.

And then pump it out into the marina?

[benzy]

Yep sorry meant to say ball valve.

Outlet is on the bottom of the tank, which does cause the issue of effluent sitting on the macerator when not in use.