Leak using black tank flush

[TitanMike]

Originally Posted by hazmat456

You cannot pressurize a black tank. They are all vented. The only danger is over filling the tank, it will usually come up through the toilet.

Or out the roof vent if the toilet isn't being flushed

[TitanMike]

Originally Posted by hazmat456

You cannot pressurize a black tank. They are all vented. The only danger is over filling the tank, it will usually come up through the toilet.

Unless the toilet is not being flushed and valve is closed. Then the black tank contents will flow from roof vent.

Technically that 7' of head will pressurize the tank to 3 psi which doesn't sound like much until you take into consideration the square footage in the tank.

Could cause a real bulge problem.

[nomad297]

I guess I didn’t need a computer.

See the difference? The plastic one has the check valve on the side outlet that goes to the tank to keep the gasses out. The brass Watts LF288A does not.

Bruce

[HistoricMustang]

Originally Posted by nomad297

You do know that is not the correct check valve/vacuum breaker for a black tank flush installation, don’t you? The brass type in your picture has only one check valve in it that keeps the potable water from a cross connection on the supply side, but it does not have the second check valve on the flush side that the “RV specific” version (the “cheap plastic” one) of that type of valve has to keep the gases (stink) from exiting the tank and venting out from beneath the vacuum breaker cap.

If you would like me to provide a cutaway drawing to show what I am talking about, let me know, and when I have access to a computer I will post it.

Bruce

Please provide the cut away drawing. Want to make sure my replacement meets the requirements that you mentioned.

I am now comfortable with all hook ups on my Forest River "Salem" FSX......just want to make sure sanitation safety is included in the Black Tank Flush system.

[fobagbob]

Originally Posted by HistoricMustang

Just confirmed...........also, these labels have been placed correctly.

The rear connection, near spare tire (threaded with screen) is City Water Hookup. Confirmed by turning off pump and opening faucet for extended period of time with hose attached.

The side connection, near door entry, is for Black Tank Flush (threaded)........this is where leak is occurring under sink in area of valve.

The other side connection is for Fresh Water Tank (not threaded).

Any comments appreciated and Thanks.

Glad that you got it sorted out. I see that the labels were changed to correct locations, but, as I am sure you already know, the caution decal under the new "City Water" label is for the old "Blank Tank Flush", it is telling you to not use the flush unless the Black Tank drain valve is open.

[nomad297]

Originally Posted by HistoricMustang

Please provide the cut away drawing.

I did. They are right before your last post.

Bruce

[HistoricMustang]

Originally Posted by nomad297

I did. They are right before your last post.

Bruce

Thanks

[HistoricMustang]

Originally Posted by fobagbob

Glad that you got it sorted out. I see that the labels were changed to correct locations, but, as I am sure you already know, the caution decal under the new "City Water" label is for the old "Blank Tank Flush", it is telling you to not use the flush unless the Black Tank drain valve is open.

Thanks for catching.....

[itat]

Originally Posted by nomad297

You do know that is not the correct check valve/vacuum breaker for a black tank flush installation, don’t you? The brass type in your picture has only one check valve in it that keeps the potable water from a cross connection on the supply side, but it does not have the second check valve on the flush side that the “RV specific” version (the “cheap plastic” one) of that type of valve has to keep the gases (stink) from exiting the tank and venting out from beneath the vacuum breaker cap.

If you would like me to provide a cutaway drawing to show what I am talking about, let me know, and when I have access to a computer I will post it.

Bruce

Thanks, Bruce. I haven’t had any odour from the black tank escape that brass Watts LF288A valve. I assumed that the vacuum relief valve is normally closed until there’s a negative pressure in the inlet side. If its normally open then there must be a low point in the hose between the valve and the sprayer nozzle that’s holding liquid and blocking gases. I’ve been pumping antifreeze in the flush line in the Fall so it shouldn’t evaporate. So far its working fine for me.

[TitanMike]

Originally Posted by itat

Thanks, Bruce. I haven’t had any odour from the black tank escape that brass Watts LF288A valve. I assumed that the vacuum relief valve is normally closed until there’s a negative pressure in the inlet side. If its normally open then there must be a low point in the hose between the valve and the sprayer nozzle that’s holding liquid and blocking gases. I’ve been pumping antifreeze in the flush line in the Fall so it shouldn’t evaporate. So far its working fine for me.

If your roof vent is clear and working properly it's a far easier path for "stinky air" to leave the tank than back through the nozzle and up into the flush hose.

Since the flow of gases from the tank is up to the highest point in theory any opening in the backflow preventer through the 1/2" pipe would actually be into the tank and from the interior of the RV.

I haven't experienced any tank odors in my TT unless I hold the toilet foot valve down longer than necessary. Then again I haven't had the valve leak and replace it with something not designed for the purpose.

[itat]

Originally Posted by TitanMike

If your roof vent is clear and working properly it's a far easier path for "stinky air" to leave the tank than back through the nozzle and up into the flush hose.

Since the flow of gases from the tank is up to the highest point in theory any opening in the backflow preventer through the 1/2" pipe would actually be into the tank and from the interior of the RV.

I haven't experienced any tank odors in my TT unless I hold the toilet foot valve down longer than necessary. Then again I haven't had the valve leak and replace it with something not designed for the purpose.

You’re forgetting about how those Maxxair fans suck air out. If you flush the toilet with the fan off its not too bad but with that fan on, wow it pulls the stinky air out of the black tank in a hurry. If there was an open 1/2” pipe from the black tank into the bathroom vanity you’d definitely be able to smell it when that fan is on a lot like ours is.

[Kevin Johnson]

Originally Posted by itat

You’re forgetting about how those Maxxair fans suck air out. If you flush the toilet with the fan off its not too bad but with that fan on, wow it pulls the stinky air out of the black tank in a hurry. If there was an open 1/2” pipe from the black tank into the bathroom vanity you’d definitely be able to smell it when that fan is on a lot like ours is.

I am so happy you mentioned this. I was having a difficult time trying to figure out why when flushing the toilet it would cause a huge stink in the trailer. We were using the max air fan to bring the cool air into the trailer.

To minimize the stink, if you open the bathroom door before flushing (or as you flush) it will not pull as much air out of the black tank.

[emm-dee]

I cannot explain why I can’t find the problem. I just opened the flush valve with the bathroom fan running. No smell. With three fans running with the valve open for two minutes and still no odors detected.

[VanWinkle]

Where did you pick up your TT? We took delivery in Indianapolis back in February. Did every one of these models come with the stickers switched? If we hadn't been watching the panel closely to see that the black tank was filling up while there was no water pressure, it would have overfilled and done damage also.

[HistoricMustang]

Originally Posted by VanWinkle

Where did you pick up your TT? We took delivery in Indianapolis back in February. Did every one of these models come with the stickers switched? If we hadn't been watching the panel closely to see that the black tank was filling up while there was no water pressure, it would have overfilled and done damage also.

Stickers were switched on my unit that was built 12/23/20. Was purchased in Savannah, Georgia.