How to check black tank vent

Ky81538 · 06-13-2013, 09:39 PM

Hi All,
New to the forum and I've been reading thru posts to try and find an answer to my question.
We have a 33 foot Hornet travel trailer. Sorry I don't have the model number and will get that next time we go up to the lake.
This trailer has been on a seasonal site since purchased new. I think it's a 2007 model. We are the third owners. We are noticing a sewer-like smell when the toilet is flushed. The black tank valve is closed, and the grey is usually left open, although I've closed it in trying to troubleshoot this issue. I've made sure there is water in all of the drains, especially the shower since we don't use it very often. I was thinking maybe the trap water had evaporated.
I've read a bunch of topics about stinky toilets and blackwater, and am not interested in a rehash of the topic. I've read about a rotating vent that is supposed to help and am considering this, but want to ensure my vent is clear first.
I suspect that my black tank vent is clogged. Is the vent directly open to the tank, or is there some kind of screen, etc in between?
I have removed the cap, pushed a 1" PVC pipe down it. It hits some kind of bottom, but isn't wet when I pull it out (the black tank was about 2/3 full). I've also tried blowing into the I" PVC pipe when inserted to see if I can blow bubbles and I cannot. I don't want to jam down hard on the 1" pipe as I don't want to cause damage. Does anyone how the configuration of this, and how can I snake it out and be sure it's clear?

**JRTJH** · 06-14-2013, 05:24 AM

The vent stack on your black tank is essentially a straight run of 1 1/2" PVC that is attached to a hole on the top of the black tank and extends through the roof on the RV. There is, as you know, a removable cap on the top. I can think of several issues you might have:

First, you may have a "dry tank" from a leaking valve. I'd fill the tank (if you don't have a black tank flush valve, just use the foot pedal on the toilet and repeatedly flush until the tank gurgles from being full. Then dump the tank and repeat with more flushing. Try to dump a full tank 3 or 4 times after filling with fresh water.

Second, you may have a vent stack that separated from the tank. ie: the 1 1/2" PVC pulled out of the top of the black tank. Twist (GENTLY) on the pipe extending through the roof, see if it moves in your hands. If it does, you may have a leaking vent stack problem. I kind of doubt this.

Third, you may (likely do) have a dirty black tank. I know this sounds pretty "sophmorish" since all black tanks are dirty.... What I mean is that since you don't tow your RV much, you may have a tank that has crud adhered to the side walls from years of use without adequate flushing at dumps. About the only way to remove this is with mechanical action (sloshing water) on the sides of the tank. It's possible that by putting some detergent (dawn works pretty good) and some Calgon (or other cheaper brand) Water softener in the tank and letting it work for a week or so while you're gone might help. Remember, for the detergent to clean, the tank must be completely full so the water is in contact with all sides and the top of the tank. When you return, dump, fill and flush several times and maybe it will help some.

Fourth, It may just be that "finally" the wind is right to push air down the vent stack and when you flush, the airflow brings a "gentle breeze" up through the toilet..... There's not much you can do about that except one of those "rotating vents" that you were considering.

Good luck. Unless there's a reason that someone has been tinkering with your vent stack, I don't imagine it's damaged, probably just an accumulation of crud and that gentle breeze. Try cleaning and flushing, hopefully it'll make your RV a little more pleasant.....

**hankpage** · 06-14-2013, 06:26 AM

You can also try running a garden hose down the vent. The hard crud John mentioned may have lodged itself in the bottom of the vent when the tank was full at one time. If the vent has come separated from the tank you will see clean water coming from under the trailer. Keep us posted as to what you find, Hank

buzzcop63 · 06-14-2013, 02:57 PM

At the risk of giving a guess at the problem that long time RV's would say "we all know not to do that", when the toilet is flushed is the bathroom fan running or a window drawing out air? If the bathroom is being vented and air is being drawn into the bathroom and the toilet is flushed air is going to come down the Black tank vent and up through the toilet into the trailer.

Ky81538 · 06-15-2013, 08:01 PM

Thanks for the replies. I'm sure that the black tank needs a good cleaning, but I am looking for more specific info here. In my original post I've asked about the connection of the vent pipe to the black tank. I've dropped a pvc pipe down the vent and I feel it did not go into the black tank. It hits something that seems pretty solid when I was expecting it to go directly into the tank. Next time I am up there I will try running some water down the vent and see what happens. I still would appreciate any further comments.

**JRTJH** · 06-16-2013, 05:27 AM

Quote:

Originally Posted by Ky81538

Thanks for the replies. I'm sure that the black tank needs a good cleaning, but I am looking for more specific info here. In my original post I've asked about the connection of the vent pipe to the black tank. I've dropped a pvc pipe down the vent and I feel it did not go into the black tank. It hits something that seems pretty solid when I was expecting it to go directly into the tank. Next time I am up there I will try running some water down the vent and see what happens. I still would appreciate any further comments.

In my first response I addressed exactly what you're now asking: If the vent stack turns, it's separated from the black tank, if it doesn't turn, in all likelyhood, it's attached and not leaking at that "vent/tank" union.

The black tank at the end the vent is attached may be only 6" deep from top to bottom. You are correct in not wanting to push too hard. The black tank is polyethylene (or another similar plastic) and over time loses some of it's elasticity and will become brittle. To start poking hard with a half inch pipe will surely get you an underbelly full of poo. If you get water flow and the vent stack doesn't fill up and overflow onto the roof with 2 or 3 gallons of water, the vent is clear and your issue is "backdraft from a dirty tank". Cleaning the tank will eliminate some of the source of the odor, not using an exhaust fan during flushing and possibly installing a swivel vent will help as well.

Ky81538 · 06-17-2013, 05:22 AM

Thanks. I will post back with my findings after this weekend. I intend to run water down the vent tube and clean the black tank as suggested.
I suspect its a combination of things as has been suggested.
Any thought on using something like drano down the vent pipe? Could it cause damage?

**hankpage** · 06-17-2013, 05:37 AM

The problem with drain cleaners is if they do not work they present a very dangerous working condition for anyone trying to repair the area that has been treated. (this comes from years of plumbing and maintenance experience) In a RV sanitary system there are too many seals and valves and other materials that could be affected by the heat and caustic effects of drain cleaners.

hankaye · 06-17-2013, 06:25 AM

Ky81538, Howdy;

Before you go making a big mess (or not), why not
break out your tape measure and see how far down
it goes into the vent pipe, then measure that same distance
down the outside and 'see' if it goes the distance to reach
the black tank. If the distance is greater then the
distance to the bottom of your doorway by several inches I
would presume that you are into the tank. Then you can
formulate a plan of action from there.
Only a suggestion ......

hankaye

campingcpl · 06-17-2013, 07:43 AM

Quote:

Originally Posted by Ky81538

Hi All,
New to the forum and I've been reading thru posts to try and find an answer to my question.
We have a 33 foot Hornet travel trailer. Sorry I don't have the model number and will get that next time we go up to the lake.
This trailer has been on a seasonal site since purchased new. I think it's a 2007 model. We are the third owners. We are noticing a sewer-like smell when the toilet is flushed. The black tank valve is closed, and the grey is usually left open, although I've closed it in trying to troubleshoot this issue. I've made sure there is water in all of the drains, especially the shower since we don't use it very often. I was thinking maybe the trap water had evaporated.
I've read a bunch of topics about stinky toilets and blackwater, and am not interested in a rehash of the topic. I've read about a rotating vent that is supposed to help and am considering this, but want to ensure my vent is clear first.
I suspect that my black tank vent is clogged. Is the vent directly open to the tank, or is there some kind of screen, etc in between?
I have removed the cap, pushed a 1" PVC pipe down it. It hits some kind of bottom, but isn't wet when I pull it out (the black tank was about 2/3 full). I've also tried blowing into the I" PVC pipe when inserted to see if I can blow bubbles and I cannot. I don't want to jam down hard on the 1" pipe as I don't want to cause damage. Does anyone how the configuration of this, and how can I snake it out and be sure it's clear?

Vent pipes do not always go straight down. I have seen in some situations (including the grey tank vent in our current unit) that it can have a jog in the pipe to reach an interior wall or a cabinet and then up to the roof. So what your piece of pipe is hitting might be a 45 degree elbow. A way to find out is use something more flexible (a garden hose, plunmbing snake, etc.) and if it hits a little resistance but then goes past with a little wiggle, I would say you was just hitting an elbow. As for the smell I would say that the tank just needs a good cleaning like other posters have said. As for cleaning the tank and what you use to do it with is going to very from one person to the next and to say one way is better than the other is hard to say. The best thing I can say is pick one of the suggestions and if that doesn't work for your situation try another till you find one that works for you. After you get it cleaned out one thing I do when I have my unit in storage is to put a couple of gallons of fresh water in the holding tank and then add my chemicals. This not only helps keep the smell down but will also help break down any solids that I didn't get out after dumping the tank before putting the unit back into storage. I wish you luck on solving your problem.

blackty · 06-17-2013, 07:17 PM

Fabric softener and hot water, lots of hot water. Let it sit for an hour and dump. I used to keep a 5 gallon Deer Park jug in the camper and dump 5 gal. in as fast as I could to rinse. Also have a clear 45 on my dump to relive my meals and make sure they all leave, again. One thing I haven't seen mentioned yet is are you sure the tank is 2/3 full, or empty with paper stuck on the sensors? Good luck...Jim

Ky81538 · 06-24-2013, 12:56 PM

Okay, I had a chance to check on a few things this past weekend, and I have to say that most of you were correct. I can run water into the black tank from the vent, so it must not be a straight shot into the tank. Ran a garden hose at full open and it pretty much took about 90 % of that, si now I am convinced that the vent is not blocked.
I flushed and flushed and flushed, about 5 times with a full tank. I ended up cutting a stick to hold the flush valve open. I also used a poo wand with the jets out the bottom and feel I knocked a bunch of stuff free. I used hot water until the water heater ran out, and then drained. I boiled water and added about 3 gallons (I know it isn't much) to the empty tank and let it sit for about an hour. Then more and more flushing.
It's funny how everyone has an opinion about it at the campground, but I welcome all suggestions.
I left the tank full for the week with about 16 ounces of Calgon water softener and about 12 ounces of Dawn dish soap. We'll see what happens this coming weekend, but the wife seemed to think it was a bit better and was cautiously optimistic.
One of the things that was mentioned is to use ONLY RV toilet paper. Do members of the forum concur with this?
Thanks for the suggestions and I will update again next week.

**JRTJH** · 06-24-2013, 01:55 PM

I DO NOT concur with using only RV toilet paper. It is WAAAAYYY too expensive and is no better than any "degradable TP"

What I mean by degradable TP is tissue that disintegrates easily. Kleenex, paper towels, etc will maintain their integrity when wet. Some TP will also maintain it's intefrity. You do not want to use those brands of TP. They will foul sensors, potentially plug valves and cause flushing/draining issues in your black tank. And, if it happens to sit in the tank when it's dry, it will form a block that's as hard as concrete and simply won't budge without mechanical removal (that means grabbing it, peeling it off the bottom and pulling it out).

The easiest way to find out if it will disintegrate in your holding tank is to put a couple of pieces in a jar, add water, shake gently and let it sit. If it maintains its integrity, you don't want to use it in your RV. If it disintegrates and becomes small bits that settle to the bottom of the jar, or dissolves and remains suspended in the water, then it is good for use in your RV. The only "solids" you want to introduce into your black tank are body waste and degradable TP. No sanitary napkins, wet ones, personal pre-moistened towelettes, etc. Just poo, pee and acceptable TP. (and of course the chemicals you prefer to control odor).

Ky81538 · 06-25-2013, 04:12 AM

Quote:

Originally Posted by JRTJH

I DO NOT concur with using only RV toilet paper. It is WAAAAYYY too expensive and is no better than any "degradable TP"

What I mean by degradable TP is tissue that disintegrates easily. Kleenex, paper towels, etc will maintain their integrity when wet. Some TP will also maintain it's intefrity. You do not want to use those brands of TP. They will foul sensors, potentially plug valves and cause flushing/draining issues in your black tank. And, if it happens to sit in the tank when it's dry, it will form a block that's as hard as concrete and simply won't budge without mechanical removal (that means grabbing it, peeling it off the bottom and pulling it out).

The easiest way to find out if it will disintegrate in your holding tank is to put a couple of pieces in a jar, add water, shake gently and let it sit. If it maintains its integrity, you don't want to use it in your RV. If it disintegrates and becomes small bits that settle to the bottom of the jar, or dissolves and remains suspended in the water, then it is good for use in your RV. The only "solids" you want to introduce into your black tank are body waste and degradable TP. No sanitary napkins, wet ones, personal pre-moistened towelettes, etc. Just poo, pee and acceptable TP. (and of course the chemicals you prefer to control odor).

What brand of TP do you use then? Our Members Mark (aka Sams Club) is obviously too thick and doesn't break down well for RV use.

Javi · 06-25-2013, 04:42 AM

We use Charmin or Charmin Ultra ...

Get an old pickle jar or something similar, fill it about 2/3's full of water and put 3 or 4 pieces of your choice of TP in the jar... close lid and shake four or five times... let sit 5 minutes..... if the TP is mostly broken up into a slurry you're good to go...

hankaye · 06-25-2013, 04:55 AM

Ky81538, Howdy;

My choice is Scott single ply.

hankaye

Roller4Tan · 06-25-2013, 11:50 AM

X2 on the Scotts

**JRTJH** · 06-25-2013, 03:34 PM

Just saw your post, we use Northern quilted at home, but it will sit UNDISSOLVED for days in a "pickle jar" so it's out for RV use. Like others, we use Scotts WHITE single ply.

Many people think an RV holding tank is a "mini septic system" It is NOT that at all. It is simply a big bucket to hold the waste until you can get it to a septic system. Essentially, nothing breaks down, nothing is "enzymatically consumed" and nothing is liquified in the "bucket". All it does is sit there, stink and wait for you to empty it. So, the longer it sits, the worse it's going to smell. I've had my tank sit for almost a month in the past, "WHEW" and when I emptied, the solids were still intact, all the "lumps and bumps" made their way through the hose just like it had been "fresh yesterday"

So, deodorize, watch what you put in the tank, use Scott's or a similar TP that breaks down and forgo the "enzymatic digesters, the liquifiers and other "high dollar" chemicals. Just use what you need to keep the smell down and empty regularly. Always ALWAYS empty a full tank, if it's not full, fill it up before you dump. Then rinse with a black tank flush or fill it again and empty a second time. Remember to put 4 or 5 gallons of water in the tank before you add deodorizer. If you pour the chemicals in an empty tank, they will flow to the dump valve, out of the tank and won't migrate back to where they are needed. So wait until the tank has a few gallons in it or just add the gallons, then add the deodorizer.

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