396 dark water tank

[norton]

when boat rocking odor is really bad ..venting proper..when pumped out odor seem to stop ..when tank is half full odor is really bad in aft state room and when it get rocked the smell really bad .. use odor control with every flush . when boat is not rocking not to bad , but does need new hoses.. any suggestion?

[mjk1040]

U can test the hoses with a wet rag. Wipe the hose with the rag and see if the smell is on the rag. Now I got to tell u that I thought we had the same issue on our 1998 355 AC/MY. It turn out to be the shower sump in the aft berth that was the issue.
Need to flush it out after using the shower. Thinking of getting a urinal cake and put in the shower sump or something on that order. Also don't forget to flush some veg oil and vinegar down the vac u flush toilets to lube ur seals keep things from caking in the system. Also, have u check the bilge in the aft cabin for standing water. If the shower sump pump isn't up to snuff, water will leak out of the sump and into the bilge. Mike

[Lyndon670]

If the smell is coming when the boat is rocking - at 1/2 full, this sounds to me like either no vent filters or blocked filters. You have already identified that you need to change the waste hoses, so I am going to assume that you have tried the rag test method that Mike suggested, and further that you have eliminated all standing water from your bilge(s).

Before you disconnect the hoses, AND ON AN EMPTY TANK, you may want to give the inside of the tank a cleaning. I pour a container of Pinesol (use the scented one, NOT the bleach smell) directly into the tank via the deck plate. Then pour in a couple of kettle's of boiling water. Once it has sat in there for an hour or so, you will want to remove one of the access plates from the top of the tank. You can remove the sender plate or if there is an inspection plate, remove that. If you have the sender plate out, it's a good time to let it sit in a bowl of CLR as well while you are cleaning your tank.

Now take a garden hose with spray gun end (I actually use my portable pressure washer) and stick it in the hole and spray around the inside of the tank. This will clean the sides an bottom of the tank. When you are comfortable that you have done all the cleaning, put it back together and get pumped out again.

[Tennessee River Rat]

I have been searching posts about the grey water system that is in our 506. I have had a real problem with them myself. Rear sump had bad float switch, that was replaced and now front sump has bad pump to replace. Which is a 3400gph pump. Biggest problem is the clothes washing machine dumping into the front sump. So I am in the process of installing a thru hull and piping the washing machine water overboard. Which brings me to my confusion, why in the world would you design a grey water system that fills up and pumps overboard? Why not have a way to suck out like black water? I told a carver engineer where I thought there head had to be when they came up with this marvelous engineering design. If we are in marina's that do not allow grey water discharge then how is this system suppose to work. Seems like a lot of extra money and weight on a boat that is not doing what it is suppose to do. Just sayin!

[nightsky]

Almost sounds like you may have a crack in the tank at about half height and the rocking causes some of the black water to rise above the crack and leak out causing the odors. Does rocking on an empty tank result in the odor too? If not, then could be a leak in the tank. If it is the rocking that results in the odors then I'm at a loss to explain that.

[Lyndon670]

Almost sounds like you may have a crack in the tank at about half height and the rocking causes some of the black water to rise above the crack and leak out causing the odors. Does rocking on an empty tank result in the odor too? If not, then could be a leak in the tank. If it is the rocking that results in the odors then I'm at a loss to explain that.

Won't need a crack for that. So long as there is air in the tank, any movement in the tank will cause the contents of the tanl to move and the smell to come out the vent hole.

Needs a vent vilter. Problem solved.

[nightsky]

Source of the post

Almost sounds like you may have a crack in the tank at about half height and the rocking causes some of the black water to rise above the crack and leak out causing the odors. Does rocking on an empty tank result in the odor too? If not, then could be a leak in the tank. If it is the rocking that results in the odors then I'm at a loss to explain that.

Won't need a crack for that. So long as there is air in the tank, any movement in the tank will cause the contents of the tanl to move and the smell to come out the vent hole.

Needs a vent vilter. Problem solved.

Well, you are right. If the problem is the filter any foul odor should come out the vent hole which is outside the hull not inside the aft cabin unless it is wafting back in (this can be checked by the owner ). If the odor is exclusively inside the boat then there has to be a "break" somewhere between the level of liquid within the tank to the vent or sanitary hoses within the aft cabin space. Maybe cracked tank, split hose or loose hose fitting.

[Viper]

Source of the post when boat rocking odor is really bad .....when boat is not rocking not to bad....

This is due to liquid movement displacing the air in the tank and forcing it out the vent. It's a normal process.

Source of the post .....when tank is half full odor is really bad in aft state room.....

Do you always have your aft windows open? It doesn't take much air movement outside the boat to force the odour from the vent back into the boat if it's blowing in the right direction. Before taking any corrective measures, try simulating the same problem but keep your windows closed if you usually don't, and see if you have the same odour in the cabin with a 1/2 tank.

Source of the post .... use odor control with every flush.....

This might be contributing to your problem. It's not enough to simply add chemicals to mask the bad odour with pleasant smells. That's all most products do. Eventually that process gets overwhelmed. I recommend trying an enzyme based product that digests the odour causing bacteria. Introducing more oxygen into the tank really helps but requires modification, usually impractical in most cases. If OEMs started using much larger vent systems, we'd all be better off.

Source of the post .....does need new hoses....

This results in a different symptom than what you are describing but you may have both problems. With permeated hoses, you'll always have a very distinct odour in the cabin that usually doesn't depend on how much you have in your tank. Even when empty, you'll still get a lingering odour that's most noticeable every time you board the boat. There are products on the market that claim to "scrub" hoses over time if used regularly but I find the only true way to eliminate the problem is to replace the hoses. By their very design, they will permeate after several years. There are some better than others and the installation makes a huge difference but if it's a flexible line rather than rigid, it will be prone to permeation.

[flyingfish]

PROBLEM SOLVED
I had the case of grey water smell. Took a week of working part time on the situation but finally have under control. My 506 has good sump pumps but the electrical connections for the motor and switch become corroded after time. Service connections and all works well. As a note. The float switches are a encapsulated mercury switch housed in plastic. just about bullet proof. So check wiring connections first. I noticed that on both of my gray tanks the vent has no filter. just open. Going today to check what i can use to filter vent before La Pue takes over

[flyingfish]

Update to grey water odor.
After some more poking around in the bilge it dawned on me why i have grey water odor. When the sump pumps became inoperative the previous owners simply removed one of the access plugs from each grey tank. When the grey tank filled, the overflow would go into the bilge. Water could then be removed by the bilge pump. This created an awfull smell in the bilge and the grey water tank would always be full, venting fluid and odor. It may have seemed like a good idea at the time but the sump pumps were not service so this condition persisted. Outcome; one mess that took many hours of flushing and repairs to get the system back into operation.