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View Full Version : back to drawing board, tying in extra holding tank



dalehollow
05-11-2014, 01:14 PM
As the regulars know my latestest venture was install a household commode, replace the straight drop, we love it. Now I need to add an extra holding tank for the commode.... My existing plastic tank does not have a acess port on the bottom side, where i assume the added tank would connect, Question: Is there a product made I can cut out an glue in a fitting to accept the standard cross over pipe to the new tank? What is it called?

Im assuming that bottom pipe would be in the 2 inch to 2 1/2 inch diameter? More importantly is this doable, I sure dont want to go back to the straight drop

My present holding tank when pumped out, is around 75 gallons according to the mark on the pump out boat tank Id like to double to around 150 gallons if that is doable thanks will look forward to thoughts tips

captrsimon
05-11-2014, 04:12 PM
You have to have a 1 1/2 npt hole at the bottom of the tank hooked up to your waste deck fitting. Just add an additional tank right next to the one you have and T off the pump out hose. No need to have the fill hose "T"ed in, the tanks will equalize in volume from the bottom hose going to your deck fitting.

dalehollow
05-11-2014, 05:42 PM
You have to have a 1 1/2 npt hole at the bottom of the tank hooked up to your waste deck fitting. Just add an additional tank right next to the one you have and T off the pump out hose. No need to have the fill hose "T"ed in, the tanks will equalize in volume from the bottom hose going to your deck fitting.

I thought the original tank needed to be connected to the new tank ....by adding a 1 1/2 pipe at the bottom of my original tank to the bottom of the new tank.
my issue is my original tank doesn't have a place to put the connecting 1 1/2 pipe. My waste deck fitting is in place on the original tank if IM following you, perhaps Im not understanding you. I did see an on line site that sells tanks and hook up kits I will call them in the morning,

42gibson
05-12-2014, 07:30 AM
I used plastic-mart for another boat.they were a lil pricey but they had a good solid tank.you can also get a fitting relocation kit from them for 28$.

captrsimon
05-12-2014, 06:51 PM
I thought the original tank needed to be connected to the new tank ....by adding a 1 1/2 pipe at the bottom of my original tank to the bottom of the new tank.
my issue is my original tank doesn't have a place to put the connecting 1 1/2 pipe. My waste deck fitting is in place on the original tank if IM following you, perhaps Im not understanding you. I did see an on line site that sells tanks and hook up kits I will call them in the morning,


Your deck waste fitting should be connected to the side of the tank at the bottom. If not how could you could pump out the tank. There should be a 1 1/2 hose either white or black coming off the side going up to the deck fitting. T into that line as close to the old tank.

easttnboater
05-13-2014, 04:15 AM
Some tanks have a 1.5 inch dip tube and pump out from the top.

I think that the bigger problem may be that he is using a conventional toilet - no macerator. I would be more concerned with the 1.5 in connector pipe getting clogged.

Endurance
05-13-2014, 06:33 AM
The good news: I wouldn't worry about the lack of macerator. I have straight-drop RV-style toilets on my boat and have never (knocking on wood) had a problem with a clog at our 1.5 inch pump out station. If anyone were going to have a clog I think it would be me. I buy my toilet paper at Costco rather than buy marine toilet paper. My friends with macerators are all too familiar with the job of clearing clogs from their toilets. Some have even learned some new vocabulary that you need if you're going to talk to clogged toilets.


The bad news: Plastic holding tanks are usually rotomoulded. Gluing to them isn't really an option. Better bet is to just replace your tank with a larger one. I would Google someone like Ronco Plastics. Plastic tanks aren't that much, especially when you consider how crappy it would be to have a leak.

OLD HOUSEBOATER
05-13-2014, 01:59 PM
Plastic welding is a mature process for adding fittings etc to poly tanks. The only problem is that there are few people good at it.

dalehollow
05-13-2014, 06:21 PM
yes take out the old an add the size tank I need, sounds better all the time didn't realize tapping into the old tank was such an issue, would not take a chance on the slightest chance of a drip.....