Holding Tank Vent Line

[Just us]

We have identified our problem as a clogged vent line. Actually the line is totally clear but the connection to the holding tank is clogged. Unfortunately the plug is an L shaped 1/4 inch piece that we can not access to poke through manually . We poured holding tank cleaner with enzymes into the line and it has been sitting on the clog for 2 weeks but has not cleared it. Is there anything else we can use that would be safe to break the clog but would then drain into the holding tank. Any ideas/advise would be most appreciated.

Just us

[S/V Antares]

If it is only 1/4 " then that is not big enough. can you replace the line? Is the 1/4 in item you speak of the overboard fitting? They sometimes they get mud wasps in them or if the screens are still there they can be salt or sh*t encrusted. If the little screens are there use a pick to pull them (it) out.

[thinwater]

Put in a new fitting hole, if you need to. You really don't need a ruptured tank. While you're at it, go at least 3/4-inch.

You can safely use any drain cleaner. I assume the tank is polyethylene. But it probably won't work.

[rebel heart]

Disconnect the hose from the plug, knock the plug clean with a wire, replace the hose? Tape some paper towels (a liberal amount) under and around the workspace to capture any funk that comes out when you disconnect the hose. I've installed and uninstalled a couple heads; it's a crap job (pun intended), but really not that bad. Just knock out and you'll be 1000x happier.

[Just us]

Thanks all for the ideas! The path from the tank side of the hose to the hull is perfectly clear. The clog is the plug coming out of the holding tank before the hose. The L
shape and the angle make it so we can't unplug it with a poker of any sort we have found. The tank is built into the keel and I believe is fiberglass. Not sure how i could add a new fitting or if I want to venture into that. The line may be 1/2 inch as well. Any other opinions on using a declogger chemical? I am able to pour into the line and have it sit at the clog?

[colemj]

Hook your dinghy foot pump to the vent hose and blow it out?

Mark

[HopCar]

I like Mark's idea of using low pressure air to try to blow it out. You really should have a bigger vent. If you have access to the top of the tank it should be pretty easy to install a second larger vent.

[mikefossl]

I hate to admit this but when this happened to us I disconnected the hose and blew out the clog with my mouth. Once the clog cleared, the pressure in the tank provided an "interesting" blow back. The dinghy pump idea sounds good.

[four winds]

Water under pressure from the outside-in through the vent opening in the hull has worked for me.

Now I do this at each pump out to keep it clear.

[peghall]

Here's a copy of the reply I just sent to your PM:

You have two problems...some muriatic acid, which you can get from any hardware store, should dissolve the blockage. It won't damage anything in the system. Follow handling and use instructions very carefully!

However, 1/4" vent is unacceptably small...we need to explore installing new one. The "standard" size for all tanks vents is 5/8"--twice the size of yours--and even that's not adequate for a waste tank 'cuz waste, unlike water and fuel, needs to be managed, not just stored.

So we need to explore how to install a new larger vent.

[GordMay]

Greetings and welcome aboard the CF, briesey.

You can’t go very far wrong, taking Peggy’s advice.

[Just us]

Hi Peggy,

Again, thank you for all of your help on this. It was your posts in other threads which helped us identify the vent line as the cause for the bubbling back air and stench in the head. I went back an measured the vent line as I was guessing previously. The vent line is currently 5/8 inch. I was mistaken by looking at the metal fitting and not taking into account the thinness of the metal and comparing it to a 1/4 inch hose line. SO hopefully we are good there. The issue is that we can't get a poker into where the clog is. So I will try muriatic acid today. How long should I give it to work??

Thank you again!

[peghall]

It should work in about an hour if it's going to. You might want to try helping it with a blast from a canned air horn.

Glad to know your vent is actually the "standard" size (which is too small for a waste tank), but we still need to move the tank fitting to a location that 's accessible...and as long as we're doing that, we might as well go all the way and replace it with 1" vent and and thru-hull that'll allow enough air into the tank to keep it aerobic AND also allow you to maintain it (backflush it regularly) to prevent any more blockages.