Holding Tank Pick up Tube

[Skipper D]

Hi

I have a fiberglass holding tank built into my hull. There's an aluminum access plate on top with IN, OUT, and vent hoses attached.

Inside the tank there was a rigid plastic (2" OD PVC PIPE) pick up tube, crudely curved to reach the lowest point in the holding tank. The pick up tube broke off flush with the access plate, most likely while underway in heavy seas.

I am considering replacing the hard PVC pipe pick up tube with a length of 1.5" sanitation hose. The hose is flexible and that should prevent a recurrence of the problem.

Is that a reasonable thing to do or should I find a way to replace the hard PVC pick up tube instead? Is there any reason not to use sanitation hose (i.e. head hose) for a pick up tube?

Thanks for your help!

 

[Peggie Hall HeadMistress]

I'd stick with hard PVC

Hose is flexible, so the end won't necessarily stay at the lowest point in the tank...you can aim hard pipe where it needs to go and it'll stay there.

I'd also replace the aluminum access plate with a sheet of 3/8" PP (polypropylene)...'cuz I think if you look very closely at the aluminum plate, you'll see that it is the plate, not the PVC pipe, that failed. Urine is so corrosive it'll even eat through 316 SS. It's not hard to make a new plate...a hole saw, some Uniseals UNISEAL (scroll through ALL the pages to see how it works and to get to the price list) and some pvc fittings, and voila--new fittings. Secure the plate with screws...seal it with a rubber gasket.

I just noticed that you're new here...welcome aboard! You'll find all kinds of info about how to use the Uniseal and replacing access plates in the discussions in this forum...and I'm here if you need more help than that.

 

[Skipper D]

The Aluminum plate did not fail. The plastic pipe broke.

I can navigate flexible hose to the lowest point and keep it there, since I can just make it long enough that it can't migrate away from the lowest point.

If I do replace the aluminum plate I will lay up a new plate out of multiple layers of fiberglass. I can lay up as many layers as is needed to make it thick enough and very strong.

Assuming that I can navigate sanitation hose to the lowest point in the tank and keep it there, is there any compelling reason not to use it instead of rigid PVC pipe?

 

[Peggie Hall HeadMistress]

You can use hose as a temporary fix, but I'd redo the whole assembly the right way the next time you sail home 'cuz I don't think you'll be happy with it over time.

I can navigate flexible hose to the lowest point and keep it there, since I can just make it long enough that it can't migrate away from the lowest point.

It would have to be pressed against the side or bottom of the tank to do that...and if it does, you won't be able to remove anything. Whether it's hard pipe or hose, the end should touch the bottom of the tank and be cut off at about a 25 degree angle to allow the most to be pulled out of the tank without risk of clogging it.

If I do replace the aluminum plate I will lay up a new plate out of multiple layers of fiberglass. I can lay up as many layers as is needed to make it thick enough and very strong.

It is possible to stretch DIY on a budget with limited access to materials too far...

All that fiberglass would be way overkill and cost you more than a 12 x 12 sheet of PP once you have access to some decent hardware stores. It doesn't have to be strong, just thick enough to tap screws and drill with a hole saw.

And as for the cost of the Uniseal, even there...they're just rubber grommets...they don't weigh anything. You could order direct from Aussie Globe online and ask 'em to put 'em in an envelope and mail 'em first class.

The builder actually didn't do that bad a job, btw...their biggest mistake was using aluminum for the plate instead of plastic. At least they didn't do what several high end trawler builders did--use SS pickup tubes, all of which have been failing and falling off in just a few years. Yours was installed exactly the way it should be done...and sounds like they copied the Sealand diptube kit (which seems to have been discontinued, 'cuz I can no longer find it on their site, but will turn up at several retailers if you google "sealand dip tube").

 

[Skipper D]

"It is possible to stretch DIY on a budget too far... "

Landed Cost for a 12X12 polycarbonate plate from America by UPS $150.00, takes a week to ten days.

Landed Cost for a 12X12 polycarbonate plate from America by USPS $60, takes 4 weeks if it arrives at all.

Assuming of course that I can find a vendor in America willing to cut and package an international shipment for a few dollars worth of material.

On the other hand, I have fiberglass material on hand where I am anchored (middle of nowhere).

It's the WORLD wide web dear, not the America wide web

 

[Joe]

Skipper......... Are you asking for advice? Or giving a test? I'v always wondered why someone would ask an expert for advice and then argue with the answer. Sounds like you have decided what you want to do already... so do it.

 

[Peggie Hall HeadMistress]

What part of...

..."once you have access to some decent hardware stores" didn't you understand?

Most Americans who cruise do come home occasionally unless they're likely to be arrested if they do. That's when I'd replace the plate. Even if you don't sail the boat home, anyone who can't figure out how to put a 12"x 12", or even 24 x 24, sheet of PP in the bottom of a duffle bag needs more help than I can offer.

 

[thinwater]

I'd be a bit concerned about wear from the hose rubbing...

... back and forth in the same spot for years. It will almost certain wear through the veil coat and allow waste into the laminate. Rubber sanitation hoses have metal which would be bad, plus they are not really meant to have the waste between the layers (minor concern). Vinyl sanitation hose doesn't have the steel wire, but I doubt it will hang down. So, as Peggy said, it's not likely to be at the bottom of the tank.

You (OP) stated that the plate did not break, the 2-inch OD pipe did.
a. Is that 1.5-inch sch 40 pressure pipe or DWV? perhaps better materials would do?
b. Did the pipe or the fitting break?

PVC tubes are quite common and breakage is rare. I suspect a good repair with good material will last for a very long time.

If there are ANY supplies available there should be PVC. If there is only what you have on board.... You know the answer.