R25OB black water tank location

[trailertrawlerkismet]

For the R25OB I’m wanting to find out how accessible the black water tank is, as well as where it is accessed from? Lastly are the overboard discharge pump, hoses n fittings in a position to be worked on if needed? I’m asking because of converting the black water tank (new n never used) to fresh water and connecting it to the house water tank by an diverter on our soon to be built RT25OB. I’m looking at installing a composting toilet to reduce pump out time, reduce odors and increase house water supply.

Jim F

 

[GTilley]

For the R25OB I’m wanting to find out how accessible the black water tank is, as well as where it is accessed from? Lastly are the overboard discharge pump, hoses n fittings in a position to be worked on if needed? I’m asking because of converting the black water tank (new n never used) to fresh water and connecting it to the house water tank by an diverter on our soon to be built RT25OB. I’m looking at installing a composting toilet to reduce pump out time, reduce odors and increase house water supply.

Jim F

Jim, it’s been a few years since you’ve done your modification to connect your unused black water tank to your fresh water tank on your R25. I’m planning on getting a waterless dry flush toilet (Modiwell R1808 RV toilet) to do the same when my new boat (2026 R25) comes in. What an ingenious way to increase your water capacity on your R25. As it’s been a few years, can you advise how that merge is holding up? Any concerns or things you might have done differently the first time around? Would love to get any input here. Thank you!

 

[Pandion]

I'm not Jim, but we've been using our blackwater tank as a freshwater tank since we bought our R27OB about six years ago, so I can give you some feedback.

If your boat is not yet in production, I'd contact the factory to see if they can commission the tank for fresh water, rather than sewage, if you intend to drink it. They may not be able to offer that level of customization, but it can't hurt to check. The issue is that the black tank is not installed with potable water in mind, so parts may be used in the install that are not NSF-rated for potable water. An example is the dip tubes, the pipes that pull the sewage from the bottom of the tank up to the pump-out fitting or over to the macerator. In our boat, those pipes are made of ABS, which is typically intended for drain-waste-vent systems and not for potable water. The same goes for the glue that is used for ABS. Here's a pic of the inside of our black tank:

In that image, you can also see what appears to be where a sliver of metal rusted on the bottom, so they may not be as thoroughly flushed before delivery.

I used a valve to make a manifold so we can select which tank our water pump draws from. It's under the galley sink where it's easy to access:

Most of the water used on the boat is for washing, showering, etc., and we're comfortable using the water from the converted black tank for that. If we need water for drinking or cooking, we just make sure we're drawing from the designated fresh tank. That works for us, but I've also been mulling over installing another water pump that will only draw water from the designated fresh tank to the cold side of the sink faucets to make things easier. Another consideration, at least on our R27OB, is that the black tank doesn't have gauge on it, so we never really know how much water is in there. One of these days, I'll add a gauge to it.

Our primary goal was to not have a traditional marine head (we went with Nature's Head), the extra water capacity was just a side benefit. 99% of RT owners get by fine on the factory capacity. But when we're away from civilization, having more good water from a known source is a benefit to us. Keep in mind you'll probably notice a difference in your boat's handling when both water tanks are full. That can be a good thing when seas are a bit sporty, not-so-much for the fuel economy, though.