Black water and Grey water tank issues

[abcan]

Hi we have purchased an Enduramax 30 MFW 2010 as a second-hand unit. It is in great condition other than the fact that we are having issues with the water tanks. We have been able to put 48 US gallons into the fresh water tank, which is good. The issue comes when we are actually using water in the unit. We found that the tub would not drain after a few days of camping. We have done some trouble shooting once we got it home. We drained all the tanks and then starting pouring water down the tub/shower in 6 US gallon increments. We were only able to pour 24 gallons down before it would no longer drain. We assumed that it was draining into the 'grey water' tank, however, when we checked the toilet drain the black tank was completely full. This means that the shower is draining into the 'sewer/black water' tank. The specs I found say the black water tank should be 54 gallons. We then decided to find out where the bathroom and kitchen sinks were draining into. We were able to pour approximately 32 gallons into the sink before it quit draining. Which would be fine except for the fact that the specs we have found say that the grey water tank should hold 54 gallons, and the gauge for grey water reads only 2/3 full. We believe that the possible reason it will not take anymore water is because the tank is not vented properly or the tank vent is plugged. We can find drain vents but no tank vent for the grey water. I really need some assistance in getting the proper specs for this unit that state what it was supposed to have when it left the factory. I am also looking for a service manual that contains the proper plumbing specs for it.

[McKannick]

Don't know much about your rig but I'll try some suggestions. Published specs agree with your expectations for the rig. There is usually a vent in the roof for each holding tank which are typically about 1-1/2 to 2 inches in diameter, with venting caps or these little wind blown 'fins' on top that encourage fume extraction as the wind blows them around. Should one of these be plugged, and you've been pouring that much water at a time down sinks and toilets, you should be hearing gurgling at the sinks as the air displaced by the inflow tries to escape where ever it can. Additionally, it's very common, particularly in the black tank, for the level sensors to be incorrect. In both tanks the sensors can accumulate crud, fouling the systems to fool the indicator as to the actual level. I have heard many people find that in certain units the sink / shower in the bath is draining into the black tank. I'm thinking that in a long rig like yours, the manufacturer may 'cheat' a bit by dumping all the local plumbing into the same tank, as for instance all the drains in your bath are going into the black tank instead of running separate pipes way back to the tank at the kitchen, which costs a few bucks more in parts and labor during assembly. Why they won't hold the expected amount, and the water is up to your toilet base indicating absolutely full, I have no idea other than the tanks are smaller than specified.

https://images.jet.com/md5/fe03ac512cddae4b298f6e7fb5933a69.1500

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[abcan]

thanks for your insight. I think this may be a winters project figuring out what is causing this issue. ;)

[Leisure Time Larry]

Hmmm, something is amiss here, and I think I have an idea.

You mean that you found the vent on the roof? One or two? The "drain vent" can be the tank vent if it splits from the drain line below the p-trap. No, I don't think that this is a venting issue. Like McKannick mentioned, the air would find a way out. If you want to try again, hold the toilet flush valve open and let it vent out of the toilet hole.

Did you ever figure out where your bathroom sink is draining to, the black or the gray?

I think your tanks are full. I find it curious that when I was looking up specs for your rig, on the same chart, the smallest model in the class, the 19MTT, specs a 28 gallon black tank and a 35 gallon gray tank. It would not surprise me at all if they installed the wrong size tanks on your unit when building it! That is worth checking out, but to do so you'll have to climb underneath and inspect your tanks. Find any markings if you can... capacity or at least a model number or something. If not, then measure them with a tape measure. Then, do the math... multiply the height x width x length of the tank in inches to get the total cubic inches. Then multiply that number by 0.004329 to get US liquid gallons.

If the tanks are different than those listed specs for your unit, then you can call Gulf Stream to raise hell with good data.

Good luck, and please let us know what you find out.

p.s. I also "assumed" when I got my rig, but I found my toilet and bathroom sink go into the black tank and the kitchen sink and shower go into the gray.

[McKannick]

You can 'raise hell' with Gulfstream if you find they shafted the buyer with smaller tanks as Larry has suggested, but 'good luck' with getting anything out of them, particularly as a second hand buyer. Even as the original, you would have had to raise hell with the dealer to get such a project as wrong tanks corrected. They would have put you off for a couple months, let your rig sit in the parking lot for a couple more months and 'maybe' would have actually swapped the tanks.
Sadly, the RV industry could care less as far as quality workmanship (generally speaking) and warranty service goes. Seems we expect the same kind of service we get with our cars at a dealership with warranty work, as in done RIGHT and QUICKLY....that just doesn't happen, generally. Unless you're dealing with the top dealers in your state you will probably not be satisfied. Tell me your state and I can tell you which are the top dealers.