Houseboat black tanks

Good afternoon Woldings,

Does anyone have any experience with replacing black tanks in a houseboat? I am wanting to increase the capacity of the black tanks on my houseboat.

i am not finding much information anywhere and not having much luck with getting what my options might be out of the marina service. Do you have to tear out the whole floor to get new tanks down in the bilge? I had heard there is such a thing as "plastic welding" where they can take the large tanks down in sections and "weld" them together.

Any information would be greatly appreciated.
Thank you for the input. I am very un-mechanically inclined so sorry for my stupidity, but i just want to make sure i understand. The suggestion is to put a couple of smaller tanks in that would fit down the access hatch to the bilge. Then place a Macerator pump that would move sewage to from the main tanks (there are already 3 tanks-1 for each bathroom) to the auxiliary tanks therefore making more room in the main tanks. Is this how it would work? What about pumping out? would the Macerator then move the sewage back to the main tanks for pump out? or would another pump out hookup to the exterior of the boat be needed? Thank you in advance for your help!


Active Member
do a search for huskey pillow tanks -- they will build you bladder tanks based on the dimensions you need. they fold up which will allow you to get them in your hold.


Well-Known Member
If you can make all tanks on the same level, all you would need is to pipe them together (waste AND vent) to existing tanks. To add remote tanks, at a higher level, you would need a macerator pump and change the pumpout fittings, to the higher set of tanks. The macerator pump would be placed in line between the lower existing tanks and the added higher tanks, and act as a lift station... Hope that is understandable.. B


Well-Known Member
I should also add that, all tanks on the same level ( within reason) would be a simpler application and less chance of malfunction. Gravity is a marvelous thing lol ... B


Well-Known Member
A macerator would allow you to pump the waste into and out of any tank you would want.

I think going in is an easy solution. We have a switch under our bathroom sink. One direction and the waste goes port. Manually turn the switch, and the waste goes starboard.

We have two separate pump outs, so that is not a problem for us.

I would think that if there was some way for you to leave the transfer switch in the "open" position, that the vacuum pump outs would pull the waste out from all the tanks if they were also plumbed together at the top. Might take a little longer to pump out, but since the macerator also grinds up everything that goes through it, there isn't much resistance.
Thank you all for the helpful tips and suggestions. I hope to get this problem fixed over thew winter as mid-week trips to DR to pump are just a huge pain in the butt!