how to open water tank inspection port

rmeador · #1 (**permalink**) 10-24-2010

I need to open up my water tank and see how bad it is, maybe clean it, and then shock treat it. I can't figure out how to open it up though. The tank is FRP, molded into the bilge. The "inspection port", if that is the right term, is a circular plate of metal (I think bronze) about 7" in diameter. There is a ring, also of the same metal, with screws regularly spaced around it, that goes around the plate. This ring appears to be sealed to the FRP of the tank (I can see something that looks a bit like butyl tape squeezing out of the seam). I don't think unscrewing these screws is the correct way to open it, but I could be wrong. There is no sign that the plate is intended to be rotated to open; it doesn't have the two shallow holes like for a deck fitting key. Also, all the hoses for the tank run through fittings screwed into tapped holes in this plate (the fill hose, 2 pressure water hoses, and the Tank Tender hose), so I don't think I can rotate it without removing those fittings/hoses. The fuel tank on my boat is set up exactly the same way, if that helps any. What is this thing called, and how do I open it? I can't find pictures online, and I don't have a camera, btw

Faster · #2 (**permalink**) 10-24-2010

Can you post a picture?

Except for the fittings described I'd be leaning towards a 'snap-in' type of plate, in which case there would be at least one indentation around the perimeter of the plate to use a tool to pry it up...

If it is threaded perhaps the intention was to remove the hoses and use the fitting to apply torque to unscrew it.

rmeador · #3 (**permalink**) 10-24-2010

I'm sorry, I don't have a camera. I really need to buy a new one (last one lost overboard), but I haven't had time. The idea of unscrewing it using the fittings to apply torque is an interesting one. I think I might give that a try, as it doesn't seem too hard to undo the hoses. I'm not sure if I could get it back together correctly though. I'm still hoping someone will come along that recognizes this from my description.

QuickMick · #4 (**permalink**) 10-25-2010

i believe i have something similar, i will take pics tonight and post manana~if they are the same you might get a little more help.

mitiempo · #5 (**permalink**) 10-25-2010

I'd remove the screws.

rmeador · #6 (**permalink**) 10-26-2010

QuickMick, I don't mean to bother you, but did you happen to get those pics? I still haven't figured this out. mitiempo, I tried to remove the screws last night with a hand screw driver and they wouldn't budge. I'd rather not try power tools until I know for sure that's the right way.

sailingdog · #7 (**permalink**) 10-26-2010

Ryan—

If you need to borrow an impact wrench to remove those screws, let me know. I've got a cordless Makita that is a gem.

rmeador · #8 (**permalink**) 10-26-2010

Thanks Dan, I'll keep that in mind. Though I have been looking for an excuse to buy an impact driver. Would I want an impact driver or an impact wrench for this job? And do you think removing the screws is the way to go, or is there some better way to open it?

hellosailor · #9 (**permalink**) 10-26-2010

rm-
Your best bet would be to post a picture, or find sistership owners. It *could* be that they used a fitting like a gas tank fitting, where there's an outer "ring" (think of a Ball canning jar, with just the ring, no lid dropped into it) that you rotate by hitting the tabs on it with a hammer. That's cheap and effective, and typically used to secure a flat "lid" with fittings in the center of it. Sound familiar?
Of course whatever they used may have just been for the convenience of the fittings, the rest may be glassed over, accidentally or intentionally, thinking no one will ever need to open it again.
For slotted screws that are stuck, I'd suggest going to Sears and getting an impact driver. Heavy tool steel, about 6" long and an inch thick, that takes hardened screwdriver (or socket) bits on one end. Twisty gizmo above that end. Then you hit the backside with a mallet, and while the "hit" forces the screwdriver bit into the slot (so it doesn't chew up the screw) the twisty bit rotates just a little, forcing the screw to unscrew.
A VERY useful tool for stuck screws and bolts of all kinds, not too expensive, usually under $20 from someplace that has a large tool inventory for mechanics and machinists. (Not Home Depot or Lowes. Sears and Harbor Fright both carry them, as do auto supply stores.)

sailingdog · #10 (**permalink**) 10-26-2010

The impact wrench is a lot easier to use and less likely to do damage than an impact driver.

Does your inspection plate look anything like this: