Sags in Tank Vent Hose

Ron20324 · Sep 25, 2018

Head pumps can pump vertical, so why not through a sag? That sag may well prevent the gook going back into the head pump.
Did you take the time to look and see WHY they brought the vent out the side?

Peggie Hall HeadMistress · Sep 25, 2018

Ron, when I read his post the first time I thought he was referring to the holding tank VENT line, not the toilet discharge line....but on second reading he may mean the toilet discharge line to the tank. As for why the fittings are where they are...if you look at illustrations of "off the shelf" holding tanks,you'll see that they all have the fittings on the side or end...inlet (from the toilet) and vent at the top, discharge at the bottom. Those are the "standard" fittings locations.

Hi John...I see you've just joined the merry band of folks who hang out on sailboatowners.com today...welcome aboard!

JonLove1949 said:
I've just cleared the forward waste tank hose and reinstalled it, but there is no way in the current configuration to not have the hose go in a downward sag. Is this going to cause me problems in the future?

Whether you're referring to the tank vent or the line from the toilet, the answer to both questions is Yes. Overfilling a tank or even heeling can cause even a half full tank to spill into the vent line. That spill will pool in any sag, effectively blocking the vent. The line from the toilet to the tank shouldn't have a sag in it either...'cuz depending on the distance from the toilet to the tank--and especially if it's an uphill run, few people flush long enough to move bowl contents all the way to the tank. Waste sitting in a low spot is likely to permeate most hose (you don't want stinky hoses!) and can also build up to become a clog.

JonLove1949 said:
Also the place where the hose goes out of the tank is not on the top, but on the side near the top. Is it worth putting a new vent in? and if so, should I just leave the old one in there instead of trying to plug the hole where the current one is?

If you're referring to the VENT line, I'd install a new vent fitting in the top of the tank...which, thanks a li'l gizmo called a Uniseal UNISEAL , is actually pretty easy to do. And if there's at least 5" clearance above the tank, moving the inlet fitting to the top of the tank would be a good idea too. Threaded plugs (available from the plumbing department at any decent hardware store) well wrapped in Teflon tape are all that's needed to seal the existing vent fitting. It may also turn out to be advisable to relocate the vent thru-hull. Even if you can't move the inlet fitting there's a way to route the line from the toilet to the tank on just about any boat.
You're welcome to send me a PM (private message...just click on my name below my picture at the left of this post) if you'd like to discuss all this in more detail than is practical in a discussion forum.

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

Peggie Hall HeadMistress · Sep 26, 2018

Good! Because I'll want to move the conversation to real email (soooo much easier than PMs!), I'll send you a PM now that includes my email address.
--Peggie

Ron20324 · Sep 26, 2018

JonLove1949 said:
Maybe because there wasn't enough clearance to go out the top, but I can fix that. I saw some instructions about installing vents that there should not be a sag. I think maybe so it can be flushed from the outside with water and it have it stay in the hose?

I'm sure the OEM vent is there for some reason. No matter where the vent ges into the tank, they will work ABOUT the same. Once the tank is full, when you pump, it will start to exit via either vent hose location. If you back-rinse from the thru hull (like I do), the hose pressure will flow into the tank. WHile at it, put in a larger vent. Remember, double the diameter is 4 times the area.

Peggie Hall HeadMistress · Sep 26, 2018

JonLove1949 said:
Thanks Ron, do you think i should back-rinse while there is still a sag in the line? It seems that would block the vent.

First, replace the "vent" thru-hull with an open bulkhead thru-hull--one you can stick your finger into AND can stick a hose nozzle against to backflush the vent line with enough water pressure to clean it out, sending everything back into the tank. That'll still leave water in the sag, but water isn't sticky and won't harden into a real blockage. Rerouting the vent line to eliminate the sag is the only good solution.

Ron20324 said:
I'm sure the OEM vent is there for some reason.

It's there because boat builders are universally the WORST sanitation plumbers on the planet. That's always been the standard location for water tank fittings, so that's where it was decided they belong when it became necessary to install holding tanks. That doesn't apply only to sanitation...they install everything in a boat hull before the deck goes on without any thought that it'll have to be replaced or maintained (new hoses, impellers etc), so they just drop stuff in anyplace it'll fit whether that's a location that can be accessed without taking half the boat apart or not. Because it's very rarely necessary to work on or replace anything until well AFTER the warranty has expired, building the boat for the lowest cost is their only concern.

(I'll get off my soapbox now...)

--Peggie

jssailem · Sep 26, 2018

Peggie Hall HeadMistress said:
Because it's very rarely necessary to work on or replace anything until well AFTER the warranty has expired, building the boat for the lowest cost is their only concern.

Rant Approved

why Engineer poorly.