Sludge in the waste tank after DIY vac pumpout

[Island Time O25]

I have a weird question or two or three.

Since I acquired the boat some years ago, at the end of each season I would get a last pre haulout pumpout as close to haulout date as possible, often just prior to leaving my mooring. And never gave my waste tank a second thought as it was installed new by PO just prior to me getting the boat.

But this season Neptune conspired against me and for several days prior to my departure from the summer mooring the pumpout boat was either out of service or not running due to high winds and waves. So we departed to my winter storage marina unpumped. I was thinking of stopping on the way to get a pump out but the weather was quite boisterous, winds on the nose at 20-25kts, gusting to 35kts and waves around 8-11ft. So I decided to deal with the 1/4 full waste tank later.

So yesterday with the help of the long hose and a dry/wet 1.5hp shop vac I managed to get whatever liquids were in the tank, about 5-7 gallons. While emptying the contents into marina portajohn I was surprised that a) it did not smell as bad as I anticipated (probably due to my splashing some enzyme treatment since the last pumpout) and b) there was little if any solid or should I say less than liquid matter.

So I got a flashlight and poked around the waste tank which is under the v-berth. What I noticed was that the lower 1/5 of one tank wall (I could not see the other 3) was darker that the top 4/5. This was also the case before I did the DIY pumpout.

Now my questions are:
1. Is it possible/probable that the smallish vac (compared to the large pumpout boat machinery) simply could not suck out more solid waste?
2. Or this was just discoloration from previous uses caked into the tank walls?
3. If #1 is there any treatment, method or way to loosen up the sludge, if in fact that's what it is, to get it pumped out with the shop vac?
4. Will the solidified sludge lying at about 1/5 of the tank's volume present any issues during the winter deep freezes here in New England or can be left as is until the proper pumpout in the spring?
Note: The winter storage marina does not have a pumpout of any kind that I know of.

The waste tank itself is a standard 35gal Todd Industries plastic tank without the inspection plate and the plumbing is more or less straightforward. Waste hose from the bowl is running through the Y valve which is zip tied at tank position to prevent overboard discharge, as well as thruhull seacock zip tied at close position. On the other side of the tank the deck pump out hose goes few feet up to the deck fitting, the vent hose just below it to the topsides and the overboard hose in what probably used to be a macerator set up going overboard via gravity and heel is permanently capped and the original outflow throughull seacock is in closed position and looks too seized to open. Otherwise all the waste thruhull seacocks are dry.

Any advice is appreciated in advance.

[sailingharry]

Some general comments.
Waste in general is not solid by the time it leaves the commode. If you watch the clear section of the pump out hose, you will see that you rarely see objects drifting by, just dirty water.
My holding tank develops a crust of very solid concrete. I think this is a continuation of the precipitate that clogs the hoses. Urine and salt water form concrete. You sail in new england, so I assume you are flushing with ocean water.
Periodically, I open my holding tank lid and vigorously pressure wash. While it is not strictly legal, I do this while running my macerator pump and pumping overboard. I feel the amount of waste that we are talking about is inconsequential.
I would not worry about what is left freezing. Freezing in an open top container, such as an inch or two of liquid in the bottom of a holding tank, does not easily create significant forces. I also suspect that the sludge will not freeze as solidly as water. And plastics are much more tolerant of freezing water than metals (from what I understand, water in a PEX pipe can freeze with no problems).

[peghall]

1. Is it possible/probable that the smallish vac (compared to the large pumpout boat machinery) simply could not suck out more solid waste?
2. Or this was just discoloration from previous uses caked into the tank walls?

Neither pumpouts nor your shop vac can get the sludge on the bottom of the tank because they can only pull out contents until level drops below the top of the discharge fitting, at which point they start sucking air. Which is why holding tanks need to be thoroughly rinsed out at least 2-3x/season...every 2-3 months if you're a live aboard and especially in preparation for winter or other extended layup. It's not a difficult job...you don't have to fill the tank with water to do it:

Now that you've gotten all but the last few inches of waste/sludge out of the tank, put about 4-6 inches of water into the tank via the deck pumpout fitting...'cuz that sends the water into the tank at the bottom to stir up sludge and hold it in suspension so it can be pumped out. Normally you'd pump that out but in your situation, use your macerator pump to to do it...repeat...repeat...till you're dumping clean water.

There will still be a few inches of clean water left in the tank, so there's one more step if there's danger of freezing: Put about a quart of antifreeze in the tank.

--Peggie

[donradcliffe]

I'd just flush a gallon of antifreeze into the tank and fugetaboutit.

[Island Time O25]

Thanks for the detailed answers. A few comments.

1. I dont have a macerator, PO uninstalled it and not kept it onboard.
2. The tank does not have any inspection plates so I have no way to get inside other than via hose holes.
3. Unfortunately I have not done what was suggested i.e. periodic flushing as I assumed the pumpouts take care of the contents.
4. I don't live aboard, yet but spend at least 2-3 overnights a week during the summer. Accordingly a can go 1-3 weeks between pumpouts depending on situation. When I have guests aboard or a party I get a pumpout the next available occasion.
5. Looks like I will leave the sludge until the spring and will deal with it then.

Peggie, is there anything other than clean water which will help to dislodge the sludge? What about vinegar or mild descaler like organic CLR?

Thanks again.

[Island Time O25]

Originally Posted by donradcliffe

I'd just flush a gallon of antifreeze into the tank and fugetaboutit.

That I do anyway after each haulout.

[peghall]

is there anything other than clean water which will help to dislodge the sludge?

I think you meant "dissolve" 'cuz once it hardens any attempts to dislodge it will result in chunks that'll surely clog the pumpout line. So I suggest you just take another run at using the shop vac to pull out the sludge while it's still diluted. Vacuuming out about 5 gal at a time isn't that bad a job.


--Peggie

[thinwater]

Originally Posted by donradcliffe

I'd just flush a gallon of antifreeze into the tank and fugetaboutit.

... and you would burst the head, because flushing antifreeze through the bowl does nothing to winterizes the entire intake side.


You have to either drain everything (it's in the instructions) or modify the plumbing to suck antifreeze through the freshwater intake.

[peghall]

Originally Posted by thinwater

... and you would burst the head, because flushing antifreeze through the bowl does nothing to winterizes the entire intake side.
You have to either drain everything (it's in the instructions) or modify the plumbing to suck antifreeze through the freshwater intake.

Which, as you know, is easy to do...just remove the intake lime from the thru-hull, stick it in a jug of antifreeze and flush the toilet.

If you've already modified the plumbing by rerouting the head intake line to tee into the head sink drain line, you only have to close the sink drain seacock, pour the antifreeze down the sink and flush the toilet.

Thanks for chiming in!

--Peggie

[GordMay]

Just because PEX can tolerate the cold, better than copper, PVC, or CPVC rigid pipes, that doesn’t mean it won’t freeze or break.
PEX pipe will expand somewhat, if frozen, and contract to its original shape, when thawed.
But, putting frequent stress on the system weakens it, increasing chances of failure and leaks, especially at connections.
So, to preserve the strength of your pipes, you should use the same standard precautions with PEX, as with rigid pipes, to keep it from freezing.

➥ https://www.flowguardgold.com/en-us/...ze-proof-pipes

“RESISTANCE OF PEX PIPE AND TUBING TO BREAKAGE WHEN FROZEN”
(FREEZE-BREAK RESISTANCE) ~ by the Plastics Pipe Institute (PPI)
➥ https://plasticpipe.org/common/Uploa...ical/TR-52.pdf