Collapsing Holding Tank

kordo

Just discovered that the vent fitting on my holding tank was too small for the hose.  My boat is a 2011, so it looks like it came from the factory that way.  Lots of sealant and the hose was compressed way too much due to the smaller diameter of the fitting.  I suggest others take a look at the vent fitting.  If it's too small it might contribute to the holding tank flexing too much or even collapsing when pumping out.  I noticed the same thing on my fresh water tank vent fitting but since there is no need to pump it out, should not be a problem.  

Michael T

Tank saver makes a great safety valve that is reasonably priced (imo) and is very easy to install on most tanks - takes about 10 minutes. Will absolutely prevent tank collapse unless some teen on a vacuum pump revs it waaay up before opening the gate valve!

Handymans342

We have all made this mod. Very easy

kordo

Michael T, I purchased a Tank Saver and will install it this Spring.  Taking a look at it, I was expecting that it would have some kind of movable valve keeping the odors in until the pump out and then opening up to avoid the tank collapsing.  There aren't any moving parts in it, at least to my eyes.  Do you now how it works?  Thanks.

Handymans342

It has a one way rubber flapper inside.

Michael T

Steve is correct it has a movable flap that is highly effective. Particularly if you have bought the brand specifically called "Tank Saver" . When some over-zealous pump-out hose jockey (often a summer teenager job) revs-up the vacuum on the septic hose the tank saver will do just that - save your tank and a nasty mess!

kordo

Thank you gentlemen.

goalie59

Not sure what all the hellabulu is all about. when I pump out the vent is the top hose that comes from the head. you can actually hear the suction in the head.no need to add a vent it is naturally already there. Just my thought. 

Liberty44140

Goalie, in my last boat that was true, gurgling in the toilet at pump out. In this boat there is no gurgling. Don’t know why. I added a vacuum release valve to my holding tank vent line before the vent filter. 

Willhound

goalie59 said:

Not sure what all the hellabulu is all about. when I pump out the vent is the top hose that comes from the head. you can actually hear the suction in the head.no need to add a vent it is naturally already there. Just my thought. 

There are several issues. The stock vent line is woefully inadequate for most powered pump outs and the toilet gurgling is a sign of that. Although it helps vent the tank, in a proper set up the toilet should not have to provide additional venting.
Also, in many of the electric pump models and conversions (like mine) the set up doesn't allow air back through the pump body to the tank. Even a manual head, if in the lock position will sometimes create an air lock and not allow air back. Our pump out operator took the time to check what kind of head I had, and even with him taking it extra slow I can see signs that the tank has been flexing and will be adding an additional vent to the tank before the first pump out this season. Should be a stock item from the manufacturer in my opinion.

Stodge

I believe the Big Orange acts like a tank saver.  It's supposed to by-pass during pump out.

Michael T

No, Yes and Yes. NO most waste tank relief valves do not provide enough safety. YES the tank saver valve should be standard OEM and YES Big Orange will provide plenty enough extra vacuum relief. 

aero3113

Is there a "best spot" to install the Tanksaver on the tank? Close to the vent? Or does it not matter?

Handymans342

Anywhere on top

aero3113

Thanks @Handymans342

Michael T

@aero3113 we usually install them where we can reach in with a drill .....but like to install away from hoses, and edges etc. and to center it in on the tank and have it in at least 6 inches from the side  to give it a more stable area. Even with a tank saver I have seen the top of a tank depress while the tank saver is "whistling" as the tank sucks air in through its valve.

Spyderweb

Just received a refill kit from Big Orange.  Here's a response on their web site from  a FAQ regarding do we need to worry about a collapsing tank once a Big Orange Filter is installed .  "The by pass valve in Big Orange only eliminates the restriction created by installing an inline filter."

Dream_Inn

Spyderweb said:

Just received a refill kit from Big Orange.  Here's a response on their web site from  a FAQ regarding do we need to worry about a collapsing tank once a Big Orange Filter is installed .  "The by pass valve in Big Orange only eliminates the restriction created by installing an inline filter."

That is because it is only connected thru the original vent line.  So, it can only maximum vent as much as the original vent line allows without a filter.

Michael T

My memory may be at fault but I'm pretty sure the Big Orange I had also had a vent built right into the filter body - not associated with any OEM  vent line - and the literature I received with it said helps prevent waste tank collapse. 

I have at least 25 acquaintances who have been using Big Orange since its inception. None, to my knowledge have ever had waste tank damage after the installation. 

Yes, I added a tank saver but I know that was overkill and I'm just ocd about that stuff. 

Dream_Inn

An excerpt from the Big Orange web site makes it sound like the filter itself is bypassed, but does not have external vent.  You are much better off adding the additional tank saver:

"Special By-Pass Valve

A potential danger of traditional vent line filters is that your holding tank could collapse when being pumped out. This happens because as the waste in your holding tank is removed, air must enter the holding tank. The way the air comes in is through the vent line.

Since the air needs to go through the filter, it is not able to come in as quickly as the pump is removing stuff from the tank. This causes the pressure to become unbalanced and the holding tank will collapse. It’s as if you were to suck the air out of a plastic pop bottle. When you suck the air out you decrease the pressure inside of the bottle, causing it to collapse.

The Big Orange Original Filter reduces this possibility by including a special by-pass valve to effectively "turn off" the filter so that you can empty the holding tank with no chance of collapse due to filter restriction."

MT, as far as 25 acquaintances having it, I know at least that that don't have it and never had an issue with collapse either.  I think we both know that it's a matter of the owner being aware and preventing the collapse issues. 

Liberty44140

I just added this in line before my holding tank vent filter. This way the vent and filter are bypassed when pumping out. Bought a Barbed 1/2” threaded T at Lowe’s and some Ss hose clamps to install it in the vent line. Very easy $20 total deal. 

https://www.homedepot.com/p/Eastman-1-2-in-MIP-Vacuum-Relief-Valve-60156/300702609

Willhound

Same as what i included on my home built odour trap. Will likely still install another in the line or maybe right in the tank itself.

skennelly

@Willhound - On your build how do you prevent activated carbon from potentially clogging the vacuum break?

skennelly

@Willhound - nevermind...sorry noticed you said something about adding one to the line as well.

Willhound

And also, I will likely mount it with the vacuum relief at the top, opposite to what the pic shows.

Dream_Inn

@Willhound , what pressure is the relief valve set at?  It looks like something I'd be interested in adding to my homemade filter as well, although I'd think mounting it on the bottom, nearest to the tank would give you best relief.  I say that because then the relief would not have to go thru the filter when needed.  Or, if filter is clogged, it can still provide relief.  (all this relief talk, I may have to go pr...oh, you get the point )

Liberty44140

Dream is right, the valve goes closest to the tank which in my case is under the filter so that air comes in through the valve during pump outs and not through the filter. 
Dream, the max psi is 150. That is before she blows. For air intake it takes little force to open it.

Willhound

Youv are correct. Valve at bottom. I got side tracked by skennely's question about the valve getting clogged. Which it won't because I'll use pellets and they'll be in a fine mesh bag.
Opening pressure is almost zero. Max pressure on mine is 200psi and promises to move 15 cfm at 2HG of pressure. 

Dream_Inn

Where did you get the valve? Part number?

Liberty44140

I posted the link to mine above, looks the same as wills but I got the 1/2”. I think wills may be bigger as mine had a spec in the box of 150 psi. 

Willhound

Mine is half inch. Made by Watts. Purchased at a Home Hardware in Canada. 
https://m.homehardware.ca/h5/m/en/r/hh/en/rec/index.htm/Plumbing-Electrical/Plumbing/Waterworks/Water-Heaters/Accessories/1-2-Vacuum-Relief-Valve/_/N-2pqfZ67l/Ne-67n/Ntk-All_EN/R-I3284653?Ntt=Vacuum+relief