Head Problem

[shamrock]

I have a new to me 82 Bristol 35.5. The holding tank was full for the fist time recently and it started leaking through the top cover of the actual holding tank. When romoving the "waste" fitting at the pumpout, I learned that there was presure buit up in the system and it started leaking out on thedeck.

the system has an air vent over the side, but I'm thinking it may be clogged?

how do I know when this thing is full and should I be concerned with the pressure build up?

Thanks!

[sabray]

Clogged vent or kink in the vent line. Should nit be pressurized. Find the vent off the tank and follow it to the hull fitting. Could be it's got a screen that is gunched up.. HAve a tank monitor so a light comes on . When a pump out boat goes by I get them to come by . In Oort jeff they have pump out boat with 250 hp merc bolted on.there is no reason they couldn't be here in 2 minutes.

[motion30]

often times when the tank becomes full the vent filter get wet and will not pass air and allowing the tank to hold pressure Check the vent line to see if it has a filter

[HopCar]

A lot of manufactures install fuel tank vents that have screens and covers. If yours is like that you should change it to just a plain thru-hull fitting without a screen.
Raritan makes a tank monitor for plastic tanks that uses sensors on the outside of the tank. It is very easy, and clean, to install: Raritan Engineering | Accessories | Tank Monitor

[peghall]

Yep...the vent IS blocked. And yes, you should definitely be concerned with pressure buildup in the system, 'cuz that can result in all kinds of nasty things...from a geyser when you open the deck pumpout fitting or an eruption in your face back through the toilet (It's gonna relieve the pressure wherever it can), to a burst tank. A blocked vent won't allow the tank to be pumped out either...'cuz without a source of air to replace tank contents as they're pulled out, the pump will pull a vacuum that prevents the pump from getting more than a gallon or two, if even that much. A particularly strong pumpout can even implode the tank.

So do NOT use the toilet again or attempt to pump out or dump the tank till you're sure the vent is open.

The two most common locations for a for vent line blockage are the vent thru-hull and the vent line connection to the tank--both the tank fitting and that end of the vent line. So start by scraping out the thru-hull with a screwdriver blade or whatever works. If there's a screen in it, knock it out...screens cause more problems than they solve. Then go to the tank and remove the vent line from it...and scrape out the tank fitting and that end of the hose.

If there's a filer in the vent line, get rid of it...'cuz it's gotten wet inside and getting wet ruins it...and also causes the charcoal to swell and block the vent. Vent filters are a horrible idea on any boat...worse on sailboats because heeling causes tank content to spill out the vent, destroying the filter and causing all kinds of problems. They also cost an arm and a leg...so if there is one, get rid of it!

Trace your vent line to make sure there aren't any kinks in it...or any sags where liquid can pool..'cuz pooled liquids in the vent create a blockage. If you find any kinks or sags, straighten out the vent and get rid of both.

Now that you've succeeded in clearing any blockage, you don't want another one...so to prevent it, backflush the vent line with the hose every time you wash the boat and/or pumpout. If the thru-hull won't let you do that, replace the thru-hull with one that will.

And, install a gauge. The Profile gauges Profile Tank Monitors are the best "bang for the buck"...they tell you how much is in the tank, not just when it's full...and also have the best customer service on the planet!

[peghall]

A lot of manufactures install fuel tank vents that have screens and covers.

They all use the same vent thru-hulls--which are all designed for fuel tank vents--on fuel, water and waste tanks 'cuz it costs 'em less to use the same ones and also because the grunt who installs 'em isn't paid to think about which one to use where.

The Raritan Tank Monitor is one of the few things they make that I wouldn't recommend to anyone...it's a knock-off the now-defunct Snake River gauge,...and way overpriced IMO. The Profile gauges are a much improved version of the same technology (external senders) for a much lower price. Check 'em out.

Practical Sailor did a test of tank monitors a couple of years ago...rated the SCAD monitors head and shoulders above any others. SCAD gauges are just a private label brand name of the Profile gauges...which becomes obvious when you compare 'em. Scad Tank Monitors Andeven MORE obvious when you call the SCAD customer service number for tech assistance and get Dennis!

[shamrock]

thanks for the advice! I'll check the vent