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Old 23-06-2021, 00:57   #1
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Holding Tank - One Pump

Hi All

I am replacing my very corroded aluminium holding tank and have opted for a poly version. Went to the manufacturers today and was very impressed with what they produce. But now I am thinking about a smart way of plumbing especially when involving the macerator. I know many prefer a diaphragm pump but in certain jurisdictions, a macerator is mandatory hence my going with that. I might have to keep a spare. The tank is low in the for'd cabin so can't gravity empty.

But that's not the question I'm asking here. The existing arrangement has a manual-pump head into the holding tank, from which a macerator pumps it overboard when regs allow. But it seems to me that the tank would hold more poo if it was macerated going into the tank.

So, I'm wondering if there' a way of utilising the one macerator pump going into the tank (from the head/WC) and then for pumping overboard. I could theoretically buy a macerating toilet but (a) I can't afford one right now and (b) there will then still be 2 pumps - WC and out from the holding tank with their associated cost and maintenence.

I this do-able? Any considered ideas or I am searching for a holy-grail in toilet terms?

Cheers
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Old 23-06-2021, 03:17   #2
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Re: Holding Tank - One Pump

Youíre not going to fit more into the tank if itís macerated, so IMHO thereís not much point to pursuing this.
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Old 23-06-2021, 03:56   #3
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Re: Holding Tank - One Pump

I agree with Sailmonkey. All *solids* dissolve pretty quickly, especially as they get smashed during the pumping of a manual head. What's in the holding tank is mainly water from flushing. Plus the poo-poo, now in liquid form.

I also think a macerator on the inlet side of the holding tank is unneeded.

But... what you are doing is thinking of ways to improve your holding tank system. Keep looking at it because you want this design to be as perfect as possible. I have yet to meet a cruiser who enjoys working on any part of his holding tank system. Make it as maintenance free as possible.

And take Peggy's advice seriously when she chimes in!

Cheers!

Steve
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Old 23-06-2021, 06:23   #4
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Re: Holding Tank - One Pump

Adding a macerator to the toilet discharge line is a bad idea for several reasons...it's also unnecessary because solid waste is already about 75% water and going through a toilet pump breaks it up, so it dissolves very quickly in the tank.

As for why it's a bad idea, even if installed in the tank inlet fitting: A manual marine toilet can only move bowl contents up to to 6' (2 meters) in the amount of time anyone is likely to spend pumping it without a lot of help from gravity. So if the tank is further than 6' from the toilet and/or it's an uphill run, bowl contents won't get to the tank until pushed along by the next flush--and maybe even one after that. If a macerator is installed close to the toilet, timing when to turn it on and off can be very challenging...if you misjudge or forget to turn it on, it can result in clog--or worse.

Bottom line: a macerator in the toilet discharge after a manual toiletis a bad idea.

Turning slightly left here...if your tank is an uphill run from the toilet and/or further than 6' from it, there are plumbing workarounds that can get the bowl contents there with minimal pumping...I'll be glad to help you figure out what to do.

--Peggie
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Old 23-06-2021, 07:03   #5
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Re: Holding Tank - One Pump

Quote:
Originally Posted by steve77 View Post

And take Peggy's advice seriously when she chimes in!

Cheers!

Steve
Yikes!

"Peggie's" not "Peggy's". Sorry for the misspelling!

Steve
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Old 23-06-2021, 16:42   #6
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Re: Holding Tank - One Pump

Thank very much all, particularly Peggie with the explanation. I see now why my idea is not such a good one and if I were smarter and had googled "What's poo made of" I would have found out it's mostly water and not wasted your time! Peggie - the head is within 6ft of the tank and there's only about 10-12" to push uphill. I'm not sure how I could improve on that?

Cheers Andy
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Old 23-06-2021, 17:02   #7
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Re: Holding Tank - One Pump

I just realised that I do have another question. The shower on my boat drains to a sealed sump with a float switch then pumps into the holding tank. As much as I understand, it's only toilet effluent that has go into a holding tank when in restricted areas. If that's right, the shower and galley sink waste can go direct overboard. So my plan is to re-route the shower to bypass the holding tank (the galley already drains direct via its' own seacock). Any thoughts on this?
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Old 23-06-2021, 17:05   #8
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Re: Holding Tank - One Pump

The shower sump should definitely go overboard, not to the holding tank.
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Old 23-06-2021, 17:21   #9
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Re: Holding Tank - One Pump

Thanks for that. Would an anti-siphon be needed in your view? The shower sump and thru-hull are both below waterline.
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Old 23-06-2021, 18:39   #10
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Re: Holding Tank - One Pump

An uphill run that short doesn't need any improvement....your toilet can easily push it that far.

You definitely haven't wasted my time...I wouldn't be here if I didn't enjoy sharing what I know and often learning something new!


Just for fun I googled "what is poo made of?" First, google asked me if I really meant "poop" and then it provided quite a list of sources with answers to that question. They all confirm that it is about 75% but also provided info I didn't know and am actually not sure I needed to know since that question isn't likely to turn up in trivia contest. But I'm prepared with an answer if it ever does!

So please feel free to ask me any questions...I'm always glad to help!

--Peggie
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Old 23-06-2021, 18:52   #11
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Re: Holding Tank - One Pump

Thank so much Peggie. I look forwards to that trivial pursuit game!
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Old 23-06-2021, 19:51   #12
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Re: Holding Tank - One Pump

Another option would be to take this opportunity to replace your heads with a Raritan Elegance which has a macerator in the head. Some others do this too but the Elegance has a bunch of other advantages. I have their smart control that reduces the amount of water used in a flush causing my holding tank to fill half as quickly.
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Old 23-06-2021, 20:30   #13
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Re: Holding Tank - One Pump

Peggie, what are the options for a relatively large uphill run? Iíve got about a 4í uphill run from Jabsco electric flush to holding tank input - if I completely empty bowl into discharge line with electric flush pump, I sometimes find the bowl refills with back flow (past joker valve) with discharge line contents. Iím assuming because of gravity push from near vertical run up to holding tank. Jeff
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Old 23-06-2021, 21:52   #14
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Re: Holding Tank - One Pump

CarlF - Very nice loo but way beyond my budget mate.
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Old 24-06-2021, 06:06   #15
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Re: Holding Tank - One Pump

FYI, my holding tank was missing when I purchased the boat last year and I am in the process of reinstalling a new (poly) tank from Ronco Plastics (the original manufacturer) and a new marine toilet to replace the existing porta-pottie.

For the toilet , I am looking at a Raritan Super-Flush if it will fit. These Catalinas came with Jabsco toilets, which IMHO are basically a plastic bicycle pump with a bowl.

I plan a "Y-valve" between the toilet and holding tank to allow direct flushing overboard via a thru-hull where permitted.

I also plan to install a 1-1/2" shutoff at the holding tank drain to isolate the tank from the pump-out hose and macerator. The valve will be closed in normal use, opened for dumping the tank then closed again. I will then flush the pump-out hose and macerator with fresh water via the deck pump-out port. My intent is to keep the pump out hose clean to prevent bad odors and to wash away the human debris from the macerator so it does not corrode.

Raritan makes a macerator control which monitors the macerator and shuts it down if running dry or locked up. A cool feature is that it will "spin" the macerator once-a-week to keep the cutting blades from corroding to the housing and seizing up. (a common failure mode for macerators.....)

https://www.amazon.com/dp/B00VUWBFTM...v_ov_lig_dp_it

I am also installing a larger diameter 3/4" vent hose for the holding tank (as compared to the original 1/2") to increase air flow to the holding tank.

cheers
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