Holding Tank Refurbish Questions

[Dollar Wine]

I have a 1986 Ticon-30, with a holding tank that is built into the hull below the V-berth. The sides and bottom are fiberglass and there is a plexiglass (?) lid with that is secured with machine screws and nuts. The lid has two access holes with 6 inch threaded plastic caps. Because of odor, vent size and other issues I decided to do the nasty job of taking it all apart, cleaning, upgrading the vent size and putting it all together again. The boat is in freshwater and I have read Peggy Hall's book.

Questions:
1) What can I use to clean the inside of the fiberglass tank and lid? There is a small amount of scale but a lot of odor.

2) What should I use as sealer on the (~ 1 inch) flange between the fiberglass tank and plexiglass lid? Would Butyl Tape be suitable? Should I roughen up the surfaces or leave them smooth?

3.) The stainless steel evacuation tube does not reach the bottom tank. Several inches of water remain after a pump out. Is this intended/desirable?

Thanks!

[peghall]

1. Since you can remove the lid, giving you total access to the inside of the tank, I'd use a power washer and a strong solution of detergent and water. Do NOT use the siphon on the power washer for the detergent...it dilutes it too much. If a power washer is out of the questions, a scrub brush (rubber gloves of course) and a strong solution of detergent (use a spray bottle to apply it undiluted) and some elbow grease.


2. I'd make a rubber gasket instead of using any sealant. Rubber gasket material is readily available at most big box and hardware stores.


3. You're lucky that urine hasn't already eaten holes in the pickup tube 'cuz it will. Replace it with a sch 80 PVC tube long enough to touch the bottom, cut at about a 25 degree angle. Any flatter will let TP and solids get caught under it, any sharper leaves too much in the tank.


You're welcome to give me a shout if you want to brainstorm further.


--Peggie

[Dollar Wine]

Thanks for the quick reply Peggie. I will give it a good cleaning with detergent. The lid is rather large, about 1 foot by 4 foot, with 26 holes for the screws making it somewhat difficult to make a rubber gasket. I thought the butyl would also seal the screws to prevent odors from seeping from the tank through the threads. Would you advise against using butyl, or is it a suitable alternative?

I need to have a look at how to replace that evacuation tube. I might have more questions after that.

Thanks again,

Dollar Wine

[Brezent]

That's a rather large access you have there. You should be able to get a large enough piece of EPDM rubber at a roofing supply place. Did the shallow pitches on my house with EPDM rubber membrane which is commonly used on commercial buildings with very low pitches. The roofing material comes in different thicknesses. I think the thicker material would be better for your situation. I see that some of the sanitary hoses use EPDM. Hopefully Peggie can verify if that material would make sense. Threw away scrap pieces plenty large enough to make a gasket for your access, so you might talk to someone who installs commercial roofs.