Is 20' too far from toilet to holding tank?

[phorvati]

I plan to run 1-1/2" pvc sch40 pipe for most of it, and have small flexible sanitation hose section on each end to absorb vibration.

[redsky49]

As long as you can maintain adequate slope, as well as avoiding any "traps", you should be okay.
You will have to pump longer, of course.

[Jim Cate]

Consider that to properly flush out that long connecting pipe you will add around 6.5 liters of extra flush water to the holding tank every time you use the loo. Means more trips to the pump out, etc.

Jim

[peghall]

Without some real help from gravity, that's about 3x as far as any manual toilet can move bowl contents. But even with enough help from gravity, you'll have 20' of pipe in which sea water minerals can build up unless you put at least a couple of gallons of fresh water through it...and 20' of PVC to search for where the wet wipe your guest flush got stuck. Between us we can find a good location for a tank that's within a reasonable distance of the toilet.

[Cheechako]

YES it is.

[phorvati]

So what do boats with two head usually do? Two holding tanks?

[NRbar]

When we purchased the boat the aft head was plumbed to the forward holding tank. I think previous owners overboard discharged at toilet instead of fiddling with the clogged long run. The amount of water needed to clear the sewer run may explain why we have a big holding tank. I took out the marine head and installed a ‘composting’ head. No clogs in a 30’ sewer run to find any more.
Rob

[Eder]

I have vacuflush heads...one of them is about 25' from black tank. Works flawlessly and uses about a liter of fresh water or less per flush.

[Lepke]

Originally Posted by phorvati

So what do boats with two head usually do? Two holding tanks?

They use sewage sumps. The farthest head or all heads drain into sewage sumps. They have a more powerful pump the can push sewage on longer runs, even to upper decks. Similar to what houses with basement toilets use.

IN plastic pipe, I'd use schedule 80. Schedule 40 fractures easy, like dropping a wrench on it.

[peghall]

Originally Posted by phorvati

So what do boats with two head usually do? Two holding tanks?

Builders, most of which are the worst sanitation system designers/plumbers on the planet, often install just one tank in an effort to save money. That wouldn't be quite so bad if they put the tank halfway between both toilet...but they almost always put the tank reasonably close to one of the toilets, and UNreasonably far from the other one. Owners are stuck with finding a solution.

A second tank within about 6' of the aft toilet is the right solution. Ronco Plastics Ronco Plastics marine Tanks makes TOP quality thick-walled water and waste tanks for a very reasonable price and has more than 400 shapes and sizes, over 100 of which are non-rectangular (which means you might be able to fit a larger one in the same space), and they install fittings in the sizes and locations specified by the customer when they make the tank.

Eder wrote: I have vacuflush heads...one of them is about 25' from black tank. Works flawlessly and uses about a liter of fresh water or less per flush.

The distance from the bowl to the tank is irrelevent. It's the distance from the vacuum pump to the tank that matters 'cuz the accumulated "vacuum" pulls the bowl contents TO the pump..the pump then has to push it the rest of the way to the tank while it's also sucking the air out of the line between the toilet and the pump...and I think you'll find that the tank isn't that far from the vacuum pump.

I've written a piece I call "VacuFlush 101" that explains in detail how it works. I'll be glad to send it to you if you'd like to send me a PM that includes your email address (no way to attach anything to a PM).

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

[J Clark H356]

The Hunter 356 has a 17 foot long line from toilet to holding tank. I have an electric Raritan Sea Era and each day flush for 17 seconds to make sure I clear the line and have just Lake or sea water in it. When I leave the boat, we flush Odorlos down the line and also leave some in the bowl. I have not had to change out my lines and my boat is on season 16 this year with 1085 days on board. If you don’t get an electric macerating toilet like the Sea Era, you will have a lot of effluent in your line. PVC is more likely to resist the odor problems, but you will still get calcification if you don’t keep it flushed along with the other potential problems pvc might being. PVC is a separate issue altogether. It would take a lot more pumps in a manual toilet than anyone is likely to do to clear a line that long.

[mikedefieslife]

Originally Posted by phorvati

So what do boats with two head usually do? Two holding tanks?

Most have one toilet with a holding tank and the other tend to flush overboard. In restricted waters everyone must use the one toilet.

[Redline452]

Yes, our SO 45.2 has two heads / two tanks. The aft head goes to a tank under the aft berth, forward head to a tank under the v-berth. Nice to have redundancy and the extra capacity. Only minus is when we go to places which charge "per tank" for pumpouts.

[Jens Jakobsen]

Originally Posted by Cheechako

YES it is.

No it is not too long. We had 30’ in our previous Bavaria 47 and it worked fine in our 16 years of ownership. Never clogged up.

[Boatyarddog]

Originally Posted by phorvati

So what do boats with two head usually do? Two holding tanks?

Lots of pumping or step up to a Vacuflush system.
Electric flush systems work ok too.
Trade off, in most cases.