Venting the holding tank - sweettank

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denisl

Member
Joined
Jul 26, 2015
Messages
8
Location
USA
Hi
Im in the middle of a complete overhaul of the sanitation system. All new trident 101 hoses, new holding tank, fittings, etc. My stock vent is 5/8. I spent a good amount of time trying to add a second vent or increasing the size of the 5/8 vent but there was really no good solution. Too much cutting would have been required to change the stock vent size. So im stuck with about 6 feet of 5/8 vent hose. Hardly ideal for a healthy aerobic environment to decompose the waste. My tank is 55gals.

My plan is to add a sweettank air bubbler system to the holding tank.

Am i right to believe that actively pumping in air to the holding tank is better than adding a larger vent hose and my 5/8 vent with the sweettank bubbler should be fine?

Thanks
 
The specs call for 5/8 or larger vent.
 
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the main reason for a tanb bubble system is for a large boat that Med Moors and the waste stench effects the other boats.

Most cruisers do not have this problem.

When we cruise we simply leave the cap off the deck discharge , no problem.

My concern would be the vent size when being pumped out.

Some waste boats and docks have a VERY strong suction system.

I would want a vent (perhaps open only when being pumped) , as large as the suction hose , usually 1 1/2 in.
 
Before you spend the money on the bubbler, see how the 5/8 works. FYI, 3/4 worked just dandy on a tank 4 times that size, but that was also a freshwater system.

EDIT and PS: It pumped out just dandy as well, on a wide variety of pump outs. Was about a 4-5 foot lift from tank to pump out fitting.
 
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A larger vent would be better but I'm with George on this. Try it with your existing vent. If you have a problem you can install the bubbler later. A lot of boats get by with 5/8" vent lines.

Wait a minute, forget everything I just said!

Yes of course you need a Sweet Tank system, maybe two.
For a minute there I forgot what I do for a living.:D
 
Too much cutting would have been required to change the stock vent size. So im stuck with about 6 feet of 5/8 vent hose. Hardly ideal for a healthy aerobic environment to decompose the waste. My tank is 55gals.



Aeration is a great solution--maybe the only solution if your tank is deeper than 18-20"...However, thanks to a li'l doodad called the Uniseal UNISEAL and Uniseal Instructions it's actually very easy to replace your vent line with a larger one. Just one cut with a hole saw to make a larger hole in the top of the tank...the right size Uniseal...and a piece of PVC pipe or a fitting from the plumbing department of any hardware store (while you're there, pick up a threaded plug and some Teflon tape to seal your existing vent fitting) to become the hose fitting....you're done. Ok...you'll also need a larger thru-hull--use a plain ol' open thru-hull--which will require using the hole saw again to enlarge the existing hole, or put in a new one, but that's not all that hard either!

When installed, maintained and operated according to the instructions, the Groco Sweetank system works! "According to instructions" means it MUST run 24/7/365 (except during any extended layup of course)...the tank has to be flushed out several times a year to get rid of any sludge...and it MAY be necessary to add a little aerobic bio-active "helper" after each pumpout.
 
HopCar said:
A larger vent would be better but I'm with George on this. Try it with your existing vent. If you have a problem you can install the bubbler later. A lot of boats get by with 5/8" vent lines.

Wait a minute, forget everything I just said!

Yes of course you need a Sweet Tank system, maybe two.
For a minute there I forgot what I do for a living.:D
Click to expand...

Get hold of yourself, Parks. Remember you have to feed Po Kitty.
 
Thanks everyone for you input and thank you Peggy for jumping in - your book has been my bible for this project.

The cutting is in the stringer holes where the existing 5/8 hose was run. Once I changed my stock white VAC sanitation hose with the thicker OD tirdent 101 hose I have hardly any space in all the stringer holes cut by the manufacture to run a larger vent hose. I was all ready to cut a new through hull for a 3/4 or 1" hole but could never get a hose bigger than 5/8 up to it (without cutting a new pathway from my tank to the through hull which would be a major project). My new tank is all uniseal fittings. I haven't even drilled a hole in the tank yet. I'm planning on running all fitting from the top of the tank and PVC as much as possible where waste could potentially sit in the hose/pipe.

My plan is to keep the 5/8 vent, run sweettank 24/7 when in water, eliminate the charcoal filter from the vent and periodically put in some KO to keep the healthy bacteria going...

The fact that none said I was crazy for running 5/8 is comforting. I already bought the sweettank system and while I have everything apart it will be simple to install. I can initially keep it off and only turn on (24/7) if I start having an odor problem - like an insurance policy at the flick of a switch.

My concern would be the vent size when being pumped out.
Click to expand...
My tank will have a tank saver valve installed as well to protect against imploding the tank from a strong pump out. Are those not reliable?
 
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HopCar said:
A larger vent would be better but I'm with George on this. Try it with your existing vent. If you have a problem you can install the bubbler later. A lot of boats get by with 5/8" vent lines.

Wait a minute, forget everything I just said!

Yes of course you need a Sweet Tank system, maybe two.
For a minute there I forgot what I do for a living.:D
Click to expand...


Well I received my Noflex Digestor from HopCar despite Park's refusal to make a personal delivery. I will report on its effectiveness in the near future. I'm not sure that this is a thread hijack as it may be quite relavent. Howard
 
Given the relatively low volume/velocity/pressure of the air that goes through the vent line, it is hard for me to understand how increasing from 5/8" would make a difference. What difference could it possibly make? I must be missing something.
 
If I read his post correctly it was not a question as to the 5/8" handling the low flow of air from the aerator but rather the high volume of liquid/solids being sucked out during tank empty process and possible "implosion". Not likely in my opinion the amount of air in that short run would just move a lot quicker.

At 55 gals. I would caution against using any disinfecting /chlorine type bowl cleaners.
 
Hmmmmm.....just reread post #1........
 
Since I always anchor, and since my tank is nearly midships, I put two 5/8" vents in my tank. One runs forward w/ a clamshell over it into the wind when anchored; the second runs aft and faces downwind when anchored.
This gives good airflow w/o any moving parts and doubles the air intake capacity for that ocasional aggressive pumpout.
 
denisl said:
Hi
Im in the middle of a complete overhaul of the sanitation system. All new trident 101 hoses, new holding tank, fittings, etc. My stock vent is 5/8. I spent a good amount of time trying to add a second vent or increasing the size of the 5/8 vent but there was really no good solution. Too much cutting would have been required to change the stock vent size. So im stuck with about 6 feet of 5/8 vent hose. Hardly ideal for a healthy aerobic environment to decompose the waste. My tank is 55gals.

My plan is to add a sweettank air bubbler system to the holding tank.

Am i right to believe that actively pumping in air to the holding tank is better than adding a larger vent hose and my 5/8 vent with the sweettank bubbler should be fine?

Thanks
Click to expand...

Our entire system is New toilets lines vent everything but tank next year I will replace the tank with a custom made 64 gallon tank

but I did increase the vent line from the old tank from a 1/2 inch to a 1 inch
 
can initially keep it off and only turn on (24/7) if I start having an odor problem - like an insurance policy at the flick of a switch.

If you'e gonna do that, return the Sweetank, 'cuz without any air pushing sludge away from the piping it'll quickly become clogged...You'll have to clean it to use it the first time. And I don't think you realize that the Sweetank can recover an anerobic tank, but it's not something that happens the minute you turn it on...it takes HOURS--an entire day or even longer, during which time the air generated by aerator pump is pushing gawdawful odor out the vent! So either commit to it or return it.

My tank will have a tank saver valve installed as well to protect against imploding the tank from a strong pump out.

Not needed. 5/8" is--has always been--the industry standard vent line size for every tank on a boat...if that were too small to stand up to strong pumpout equipment, the industry standard would have been upgraded to a larger diameter a couple of decades ago. Pumpouts only implode tanks that have BLOCKED vent lines...in which case it wouldn't matter if your vent was 2".
 
ulysses said:
At 55 gals. I would caution against using any disinfecting /chlorine type bowl cleaners.
Click to expand...

Don't use them if the tank were only 2 gallons or even if the toilet only flushes directly overboard. Chlorine is highly destructive to the rubber parts in toilets, breaks down hose resistance to odor permeation...kills the bacteria in a tank that's needed to break down solids and TP and when combined with vinegar produces a gas that's even more toxic than combining chlorine and ammonia. NEVER use ANY household chemical bowl cleaners, Lysol, pine oil cleaners, bleach or any petroleum based product in a marine sanitation system.
 
HeadMistress said:
Don't use them if the tank were only 2 gallons or even if the toilet only flushes directly overboard. Chlorine is highly destructive to the rubber parts in toilets, breaks down hose resistance to odor permeation...kills the bacteria in a tank that's needed to break down solids and TP and when combined with vinegar produces a gas that's even more toxic than combining chlorine and ammonia. NEVER use ANY household chemical bowl cleaners, Lysol, pine oil cleaners, bleach or any petroleum based product in a marine sanitation system.
Click to expand...

One of the first investment we bought was Peggy's book just amazing her knowledge

Our decision to change heads and entire system came after the forward head broke for the 4th time in 3 months old and worn out and raw water flush ( a bit smelly)

After replacing everything but the tank and vent line , we noticed the 1/2 vent line collapsing during pump out ( this was after we replaced the top seal on the tank it was leaking

Then I replaced the old vent and vent line after the new line did not supply enough air

Next will be my custom larger tank
 
Could you run a second 5/8" hose through those existing cut outs?
-------------------------------------------------------------------------------

I, too, did that. One vent line out the port side, one vent line out the stbd. side.

It's not perfect as I still need a de-odorizer but not bad.

I do also use the charcoal filters but I've cut and modified them using a pvc union so they can be reused/recharged. The union is offset to one end as far as it will go so repacking will be easier.

I though it was ridiculous to toss the old filter and then pay $100 - $150 per filter.
 
On a previous boat I had good luck w/ a second vent that was short and straight... bends & length are an enemy.
Take a look at my website - I have added a bubbler and very satisfied w/ the results.
Bacchus website
A LOT less $ than the sweettank system...
Don
 
I'm perfectly happy running the sweettank 24/7 - that's why I bought it (for $230). In the grand scheme of things the sweettank is a small investment. Thanks Peggy - I didn't think about how the aerator would get fouled over time with sludge. I surely don't want to clean that. It will be installed and used!

My initial post was not about the worry of the vent during pump out - rather the good flow of oxygen into the holding tank to promote aerobic decomposition of the waste and prevent the stink of a tank going anaerobic (as I learned from Peggy's book).

I tried to increase my vent size but believe it or not, a 3/4" hose simply could not be snaked up through the exiting cutouts in the boat after I moved to the larger OD trident 101 hose (sharing the same cutouts as the vent). The Trident is considerably larger in OD and it took a fair amount of force to pull the new 5/8 vent hose through the cutouts - good thing for the nipple and PVC cement holding the old and new hoses together.

I do have a second 5/8 hose "pre-run" to the port side of the boat but I haven't figured out a way to reach the side of the hull to attach a hose clamp for a second vent fitting. Maybe someday I'll find someone with long arms and have a stbd and port vent - but for now, stbd 5/8 looks like it will do...

Peggy - one more question, this time about the uniseal. I planned on putting all my fittings on top of the tank but I just got back from the boat to dry fit everything and the clearance between the deck and top of the tank is too tight. I'll have to put some fittings on the side of the tank. Would you be comfortable with putting a uniseal fitting below the waste water line? I may have to put one on the bottom of the tank for the macerator pump out port (the dip tube is too high on top of the tank).
 
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So, my suspicions that the charcoal filter is useless are sort of true? I was thinking about changing it. (unknown how old it is, or how long it's been installed) Debating if 230 is worth it for a bubbler. One of the downsides to having an MSD.
 
My initial post was not about the worry of the vent during pump out - rather the good flow of oxygen into the holding tank to promote aerobic decomposition of the waste and prevent the stink of a tank going anaerobic...

With an aerator installed, the vent ceases to be needed as a source of oxygen...that becomes the aerator pump's job. The vent now only provides an escape for air in the tank and asource of air to replace tank contents as they're pulled out by a pumpout or overboard discharge pump.
 
New holding tank design

I will be installing a blackwater tank of about 140 gallons in the bow under the head area. Where can I find guidelines on proper design and use?
 
Would you be comfortable with putting a uniseal fitting below the waste water line? I may have to put one on the bottom of the tank for the macerator pump out port (the dip tube is too high on top of the tank).

ON the bottom? or AT the bottom? Unless your tank is entirely above waterline and you plan to dump at sea using only gravity, I would not put a discharge fitting ON the bottom of any tank. Sludge will pack the discharge line unless you're scrupulous about flushing out the tank and plumbing almost every time you pump out or dump.

You can use a Uniseal for a connection AT the bottom of the tank ONLY if there is -0- stress on the fitting in it to either side or up or down that can break the seal.
 
cappy208 said:
So, my suspicions that the charcoal filter is useless are sort of true? I was thinking about changing it. (unknown how old it is, or how long it's been installed) Debating if 230 is worth it for a bubbler. One of the downsides to having an MSD.
Click to expand...

I wish I could have invented a product that actually helps to create the very problem it’s sold to solve, because that’s what a vent line filter does. Filters do trap the gasses which try to escape through the vent line, but they impede the free exchange of air needed to prevent odor from forming in the first place, eliminating the need for a filter! They only last about a year, are toast immediately if they get wet--which makes it impossible to backflush the vent line to prevent blockages--and ridiculously expensive. So install a vent line filter only as a last resort, because gasses that can’t easily pass through the vent line will go wherever they can-into hoses, eventually permeating even the best ones.
 
denisl said:
I'm perfectly happy running the sweettank 24/7 - that's why I bought it (for $230). In the grand scheme of things the sweettank is a small investment. Thanks Peggy - I didn't think about how the aerator would get fouled over time with sludge. I surely don't want to clean that. It will be installed and used!

My initial post was not about the worry of the vent during pump out - rather the good flow of oxygen into the holding tank to promote aerobic decomposition of the waste and prevent the stink of a tank going anaerobic (as I learned from Peggy's book).

I tried to increase my vent size but believe it or not, a 3/4" hose simply could not be snaked up through the exiting cutouts in the boat after I moved to the larger OD trident 101 hose (sharing the same cutouts as the vent). The Trident is considerably larger in OD and it took a fair amount of force to pull the new 5/8 vent hose through the cutouts - good thing for the nipple and PVC cement holding the old and new hoses together.

I do have a second 5/8 hose "pre-run" to the port side of the boat but I haven't figured out a way to reach the side of the hull to attach a hose clamp for a second vent fitting. Maybe someday I'll find someone with long arms and have a stbd and port vent - but for now, stbd 5/8 looks like it will do...

Peggy - one more question, this time about the uniseal. I planned on putting all my fittings on top of the tank but I just got back from the boat to dry fit everything and the clearance between the deck and top of the tank is too tight. I'll have to put some fittings on the side of the tank. Would you be comfortable with putting a uniseal fitting below the waste water line? I may have to put one on the bottom of the tank for the macerator pump out port (the dip tube is too high on top of the tank).
Click to expand...

I don't think I would use a uniseal permanently at or below a liquid level...put an access plate on the top and a regular through hull at the bottom of the side of the tank. See if you can also put the overboard discharge pump hose downward to a low spot so the tank drains and the overboard pump can get it nearly all out of the tank.

My boat is set up that way and it hasn't had a problem yet....and I am not anal (pun intended) about flushing after pumping.

Not to say it may not be a problem for you and your use of the holding tank....but boats and their systems can be compromises.

I think the trick is to never let your tank even start to dry out.
 
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I just picked up something else in denisl's post:I may have to put one on the bottom of the tank for the macerator pump out port (the dip tube is too high on top of the tank).

Despite the fact that Jabsco shows their macerator pumps connected directly to a tank, I'd never do that...because you never discover that the macerator isn't working when a tank is empty, only when it's full. If the pump is connected directly to the tank, there's no way to remove it without dumping your tank into your boat. I always recommend installing TWO discharge ports in a tank--one directly to the pumpout fitting, the other directly to the overboard discharge pump and thru-hull with a shutoff valve at the tank. This has the added advantage of eliminating a y-valve.

I think the trick is to never let your tank even start to dry out.

No...the trick is to MAINTAIN the tank and plumbing, which includes flushing it ALL out 3-4 x year, leaving only a 1/2" of clean water om the bottom. Macerator pumps should be at least nominally rinsed after EVERY use if you don't want the impeller to become firmly stuck to the inside of its housing...often resulting in a cracked vane the next time you try to use it.
 
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Doesn't happen to my macerator pumps.

I guess living aboard and using the system like an engine helps.

You can have just one port with a tee and manage the through hull during pumpouts if 2 ports would be an issue.
 
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I dont know what hose is being used for the 5/8 vent line, but couldnt you just use a 5/8 fuel line to keep from having it collapse?

Could you use a additive like this for smells? It works great in my rv's 40 gallon tank.
k2-_8d2fe045-d13c-4b8a-a920-d84dcb23d6d1.v1.jpg
 
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