Replacing a Holding Tank on GB 42 Classic

[JESSEDIVER49]

I am in the process of replacing the leaky 30+ yr old mild steel holding tank on my Grand Banks 42 Classic and have a removal problem. The company I hired to do the removal and replace with a plastic tank I bought from Ronco can't get the old tank out. They removed all the wood 2x2s top perimeter and at the corners, verticals, and yet the tank seems to be bonded underneath. Using a mirror, I can see it lies on two longitudinal supports and I see no evidence of it being fiberglassed in. To anyone who has done this change-out before, I'd appreciate some light on this matter. The company I hired now proposes to remove the top of the old steel tank, sawzall cut, and place the new plastic tank inside the steel shell since the plastic tank is a couple inches less in size length and width. Since all connections are on the top, with proper lateral support between the metal and the plastic, seems like a reasonable solution. Comments?

 

[Woodland Hills]

Why not use the sawzall to cut up the tank once you get access by removing the top? Of a cutoff wheel in a hand held grinder if the saw is too large. Better to remove it now if you can.

 

[Nightsky]

Tank outlet at the top? with down pipe to just off bottom of tank? Or will they cut out one end of the old steel tank to allow access to the tank outlet at the bottom of the tank?

 

[Xsbank]

So who gets to clean out the old tank to put the new one in it? Barf.

Get it all out of there, it will rust away and make a mess forever, plus life is too short to clean it.

Also, hoping Peggy will chime in but bottom discharges are less trouble than top but make sure if you use the bottom one that the hose slopes away from the tank so it will not hold poop and permeate rapidly.

 

[Russell Clifton]

I would think it might take months or years to get rid of the smell if you left the old tank in with the top cut off. Just cut the whole thing out of there.

 

[Comodave]

I would also get the old tank out. It may take a lot of sawsall blades or a grinder with a cutting wheel, but they should be able to get it out one way or another. As said, it will continue to rust and smell.

 

[HeadMistress]

Get it all out of there, it will rust away and make a mess forever, plus life is too short to clean it.

I definitely agree with that!

... bottom discharges are less trouble than top but make sure if you use the bottom one that the hose slopes away from the tank so it will not hold poop and permeate rapidly.

But I definitely DISagree with that! A discharge line at the bottom of the tank to a deck pumpout fitting will fill with tank contents to the level in the tank. A line that slopes down from a discharge at the bottom of the tank eventually has to go up to the deck fitting...it'll fill with tank contents all the way to that turn and beyond. A "P-trap" in that discharge line MIGHT allow a bit more to be pumped out, but that's all it can do...meanwhile it will stay full of tank contents.

Otoh, putting all fittings on the top of the tank instead of on the side or end not only increases the number of flushes that the tank can hold, leaves no sewage standing in any line. A pickup tube inside the tank long enough to touch the bottom and cut diagonally about 25 degrees (any sharper leaves too much in the tank, flatter can trap undissolved solids and TP under it) leaves less in the tank than is possible from a discharge at the bottom no matter how it's plumbed. When fittings are on the top of tank that can also be dumped at sea, TWO discharge fittings--both with pickup tubes of course--eliminate the need for a y-valve in the discharge line.
However, 1.5" fittings need at least 5" clearance above the tank, which isn't always possible. In which case, the only good solution for a discharge fitting at the bottom of a tank is to run sch 80 PVC from the discharge fitting to the top of the tank, then switch to hose.

Peggie
"If you can't explain it to a six year old, you don't completely understand it yourself." --Albert Einstein

 

[SoWhat]

Get it all out of there, it will rust away and make a mess forever, plus life is too short to clean it.

Sound advice. I don't understand how a professional can have a problem removing a small metal tank. Give me an angle grinder and a sawzall and I'll eventually have the Golden Gate Bridge in pieces.

If the holding tank wasn't completely emptied at last pump out, then use a hand bilge pump and a 5 gal gas can (along with rubber gloves, half face mask with canisters, plenty of krud kutter, downey, bleach, etc.) Rinse and repeat.

 

[Marlinmike]

I didn't even read any responses and I was thinking the same thing most stated, get the whole thing out of there, most likely 5200 in...?