Community Forums

PJinHawaii · 10-26-2011, 08:43 PM

Embarassingly Silly Question #6 : Black water valve open or closed with hookups?

Another newbie question...

On a recent vacation with a rental RV, (part of our pre-purchase research), we enjoyed full hookups at several of our stops.

When your hooked-up, do you ever leave the valves open and allow the waste (black and/or grey) to go to sewer directly and continuously? or do you let the tanks fill and then go out and pull the valves to dump only as needed? And why do you do it the way you do?

As a side note: It seems to me, that there is no advantage to using direct connect water, (as opposed to our tank) unless your dump valves are always opened, since your still limited by the capacity of your waste water tanks. In fact, if we used water from our fresh water tank, we could be guaranteed that we wouldn't over-fill the holding tanks because the capacities are matched right?

And one more thing... what happens if you over fill the grey water tank? or the black water tank? (those unreliable waste tanke level sensors sure make it seem like an accident waiting to happen...)

PJ in Hawaii

GMRHost · 10-26-2011, 08:58 PM

When I "hook up" I've always kept the valve closed and opened it to drain it once daily. It's only a personal preference, but I feel better not leaving myself open to whatever "gases" are in the CG sewer.
Running on site water usually means better pressure and less wear and tear on the pump, but that again is preference, not a mandate.

bldrbob · 10-26-2011, 08:59 PM

If you leave the black valve open the liquid leaves and the solids stay behind. Not a good thing.I leave the grey valve open till almost ready to dump the black . Then I close grey so I have some rince water for the hose.When the toilet burps when flushing it is time to dump the black.If the grey valve is closed a good indication that the tank is full is when you see water in the shower.

JimM68 · 10-26-2011, 09:04 PM

I dump when full. Takes 2-3 days without conservation.

When the gray tank is full, it overflows into the shower, when that's full it goes on the floor.
Black does the same, but in the toilet.

Tank level sensors rarely work, but after a while u get to know your coach and it's passengers, and how much water they hold / use.

On the fresh water... I fill the onboard tank with good water from home. Whenever possible I use the campgrounds water, and keep mine. If the campgrounds water is too nasty to use, I unhook and turn on the water pump.

I never fill the tank from campground water until i'm sure it's good.

Wolfpack Fan · 10-26-2011, 09:05 PM

Quote:

Originally Posted by PJinHawaii

Embarassingly Silly Question #6 : Black water valve open or closed with hookups?

Another newbie question...

On a recent vacation with a rental RV, (part of our pre-purchase research), we enjoyed full hookups at several of our stops.

When your hooked-up, do you ever leave the valves open and allow the waste (black and/or grey) to go to sewer directly and continuously? or do you let the tanks fill and then go out and pull the valves to dump only as needed? And why do you do it the way you do?

As a side note: It seems to me, that there is no advantage to using direct connect water, (as opposed to our tank) unless your dump valves are always opened, since your still limited by the capacity of your waste water tanks. In fact, if we used water from our fresh water tank, we could be guaranteed that we wouldn't over-fill the holding tanks because the capacities are matched right?

And one more thing... what happens if you over fill the grey water tank? or the black water tank? (those unreliable waste tanke level sensors sure make it seem like an accident waiting to happen...)

PJ in Hawaii

Leave your valve closed on your black tank when you're on park hook ups. Drain it before you leave if it's a short stay or more frequently if you're staying a while. After you drain it fill the toilet bowl a couple or three times and put some water back into the tank. If you leave it open, the liquid waste will drain out continuously causing the solid waste to stick to the bottom of the tank worse than otherwise.

As far as what happens when it gets full. On the gray side your shower will appear as though it's clogged and won't drain. Same for the toilet. It's a sure fire way to know it's time to dump for sure.

Your question isn't a silly question all. The silly question is the one your afraid to ask. There's good folks on this forum that are glad to give experienced advice. I don't think I've ever seen someone reply "that was a silly question".

Tyler6357 · 10-26-2011, 09:15 PM

You should always keep the black water tank closed and dump it after it gets at least 1/2 full or before you get on the road. You want the waste to have some water to float in with plenty of water to flush it when you dump it otherwise it might stick to the bottom of the tank and start to dry causing terrible smell and difficulty cleaning it out. It is a good idea to keep the grey water tank closed and let it fill up some too before you dump it. I do this to clean the hose out after I dump the black water tank. Always dump the black water tank first and then dump the gray water to flush out the hose with the cleaner water. Make sure that you put some freash water back in the black water tank after you dump it before you use the bathroom. Also, if you over fill the black or gray water tanks it will start to back up into your toilet or sinks respectivly. Also, if you use a water hookup you won't have to use the water pump to pump it out of the freash water tank, you will generally get bettter water pressure if you use a water hookup depending on how good of a water pump you have. Its a good idea to carry a pressure valve with you so that you can limit the water pressure from your hookup or else too much pressure could blow the seals around the sinks and shower. Some hookups have quite a bit of water pressure, too much for your seals to handle. Also, most coaches are set up so that the water hookup will fill up your fresh water tank so that you don't have to fill up the freash water tank from the side if you have a water hookup.

historyljc · 10-26-2011, 09:25 PM

When I use my 3" drain hose I use one of the hose carriers that is higher on one end and lower on the drain end. I allow a half loop where it attaches to the coach drain system. That gives me a "p trap" that fills with water so that I can leave the grey tank open and not fear sewer gases or other stuff coming in by the hose. Leave the black tank valve closed unti the tank's at least 3/4 full so that you get a good "rush" of water when you open the valve that will take to solids along with the liquid.

RickO · 10-26-2011, 09:31 PM

Good advice so far. Not silly questions at all.

Never (as in... never never) leave your black tank valve open. I leave our grey tank valve open sometimes but usually keep it closed so my tank gets the benefit of the "whoosh" when a nearly full tank is flushed.

Don't dump the black tank until it's >2/3 full for the same reason. If you want to dump before that, add fresh water to make it 2/3 full. And then it's a good idea to have a nearly full grey tank to dump through your hose after dumping the black water to flush out the "stuff".

Add as much fresh water to the black tank as you feel comfortable with after flushing. The more water the better. I go a bit overboard and usually add ~15 gallons but I have a 57 gallon black tank so have the room.

Don't assume the waste tanks and fresh water tanks are matched to avoid over filling one of the waste tanks! It may well be that you have more combined waste storage than fresh water capacity but that won't keep you from over filling the grey tank while there is still a lot of room in the black tank.

Good luck and keep us posted on your adventures.

Aloha

Rick

PJinHawaii · 10-26-2011, 09:39 PM

Quote:

Originally Posted by bldrbob

... When the toilet burps when flushing it is time to dump the black. ... .

When it Burps? Hmmmm, interesting description. I'm having a hard time picturing that in my mind's eye. What is that like? Will there be splatter? (sounds unpleasant... like something that should be avoided)

PJ

RVNeophytes2 · 10-26-2011, 09:59 PM

Quote:

Originally Posted by JimM68

I dump when full. Takes 2-3 days without conservation.

When the gray tank is full, it overflows into the shower, when that's full it goes on the floor.
Black does the same, but in the toilet.

On the fresh water... I fill the onboard tank with good water from home. Whenever possible I use the campgrounds water, and keep mine. If the campgrounds water is too nasty to use, I unhook and turn on the water pump.

I never fill the tank from campground water until i'm sure it's good.

Some great ideas, Jim. Carrying "good" fresh in reserve is a stroke of brilliance.

My owners manual says add 5 gallons of water to the black water tank after emptying. You want to float the solids -- and then drain only after you have enough to shove the business down the hose. After that -- here comes the fun part -- send the gray water through to blast the hose clean. Of course, this all requires keeping the slide valves closed, sometimes for days at a time.

paz · 10-27-2011, 06:28 AM

Quote:

Originally Posted by PJinHawaii

When it Burps? Hmmmm, interesting description. I'm having a hard time picturing that in my mind's eye. What is that like? Will there be splatter? (sounds unpleasant... like something that should be avoided)

PJ

When flushing, the air in the tube below the toilet normally gets forced into the black tank ahead of the flush. The air then escapes through the vent. When the black tank fills to the bottom of the tube that drains the toilet into the tank, the liquid in the tank forms sort of a seal at the bottom of the tube. Since the air can no longer escape up the vent, it "burps" back up through the toilet. The bubble that comes up is noticeable, but the volume of air in the tube is not large enough to make a big splash.

JOMARFL (FMCA 401058) · 10-27-2011, 06:42 AM

okay next time I burp I'm going to remember this post

IC2 · 10-27-2011, 07:30 AM

I guess that must be a specialty item as the half dozen trailers and 5ers that I've owned over the past 30+ years do/did not "burp" nor bubble back when draining either tank.

Not to make light of that, my guess is that if your tank(s) has that malady, you might want to look at the roof top vent to make sure it isn't plugged at least partially.

Senior Chief · 10-27-2011, 07:56 AM

Quote:

Originally Posted by IC2

I guess that must be a specialty item as the half dozen trailers and 5ers that I've owned over the past 30+ years do/did not "burp" nor bubble back when draining either tank.

Not to make light of that, my guess is that if your tank(s) has that malady, you might want to look at the roof top vent to make sure it isn't plugged at least partially.

The black tank doesn't "burp" when you drain, but it does when the tank is just about full to the top. I don't believe the gray tank (at least not ours,) does this. It's actually more of a "blup" than a BURP, anyhow.

When its full, the bottom of the vent is submerged, and any trapped air must come back up the toilet pipe, hence the burp.

Ours gets a bit "whiffy" when its full (again, because the bottom of the vent is submerged) which is our signal to dump the black.

OP don't be concerned about splatter or icky if you follow this method. It works effectively, and dumping the black when its full is better for the long term health of your tank.

You will NOT want to live through the tedious removal of the dreaded Brown Pyramid