Waste/fresh water emptying problem

Perhaps you are slightly nose down on your pitch? If it comes out when you level it up on a slope then this seems logical.

Re grey waste water, possibly sediment at bottom of tank?  We learned never to let big particles into our waste tank, we use a wash up bowl for rinsing and pot washing. In essence, the only thing that goes into our waste water tank is hand wash water and shower water. It keeps things fresher and flowing better. Quite surprising how easy the pipe work blocks occasionally, so better prevention than cure. 

Have a look underneath ad well for any kinks or drops in pipes. 

 TDA is doing well if every bit of food/fat can be stopped going into the waste tank. I carry an old bit of TV coaxial cable in my locker which I can stuff up the waste outlet to clear any blockages. I suggest you put a dose of tank cleaner in the tank and go for a drive to shake it about before emptying. I do that a couple of times a year, keeps the smells away and the blockages at bay and there is always the bit of coax to hand if necessary

peedee

We don’t put dish water into the tank at all, PD, so we're doing well too. It's easy enough to avoid. Have a bowl and carry it to a disposal point or hedge (with permission, naturally).

notwithstanding any 'blockages' (but being able to drain when at home suggests otherwise) ill guess its to do with layout of the water systems.

ideally, tanks should be close to their purpose....ie our waste tanks is directly below our central kitchen/washroom so water enters easily as the pipe runs are short and near vertical....

for emptying, the start of the drain pipe is at the low point of the tank (deliberately designed to help clear all the water) and then there is just a short run to the output end, slopes dont affect drainage much.

however, some vans have tanks seemingly placed as afterthoughts, often at the opposite end of the van to the outlet...which is where slopes  and long pipe runs can impact on the drainage far more....

however, with a decent amount of water in a tank, there should be sufficient 'pressure' to force water out, even on a long, slightly uphill journey.

by all means try the 'coax/hosepipe up the drain' method to try and clear any blockage, but also have a look under the van and 'check the plumbing'....might provide a clue.

May as well go to a dish washing area inthe first place if you are going to do that. I like an easier life than that, visit the MV waste disposal point when leavingand open the valve. I do the same if no disposal point but into a couple of collapsble buckets.

peedee

Not at all. Our water is hotter than site supplies and why carry a load of dishes around the site? Not all sites have dish wash areas and what's difficult about getting out of the van and taking a bowl of water to a drain or hedge? 

I could make the same negative observations regarding waste water disposal and carting buckets around. A hose piping it to a drain or hedge is much simpler.

Each to their own, eh?

Tend to agree. We try and minimise it by wiping any excess oil fat / debris off pans / plates with kitchen paper. Not tremendously environmentally friendly but very effective. Any solid debris we miss are caught in some strainer things in the plug hole. If a pan is particularly messy I take it to the pot wash, as I do with the cadac.

We try and pitch near a service point so washing up water can be disposed of easily. If that is not possible I pour it into our wheeled waste water container. With the current restrictions on Club sites it could be quite inconvenient to try and use site facilities.

It would seem the OP has a partial blockage somewhere between the tank and the exit point. I suspect the OP will either have to disassemble the pipework from the tank or use Peedee's method. Probably a regular application of tank cleaner would help keep the system clean and blockage free in future?

David