My toilet and shower water smell like rotten eggs or methane or, excuse the crassness, but a fart 
I live in a brand new park model rv, with rv plumbing I suppose ( it's more exposed, not like a stick built ), and NO holding tanks, just regular black pipes to the sewer line. I've recently been smelling the coming from the toilet presumably, and also in the shower water. The park uses well and city water. They had plumbers out to clear the mainline maybe a month or 2 ago. I know this because they had a giant snake like a water hose reel....and my toilet was gurgling prior to them snaking the main line. The park is old, like really old, pre-1950's if I had to guess. l have a w/d hook up that has never been used, the contractor said it had a leak that needed repair (another issue for another day). I recently went to a plumbing store and the guy gave me a valve and hose to connect to the hot water line so that I could connect my dishwasher. The is no vent for it up top on the sink, nor is there a loop in the drain line, not sure if it matters, but I'm trying to give as much info as possible
Also, I have an electric water heater. Its plumbed for natural gas, but only the stove uses it, and I'm pretty sure it's not a gas leak. There's an exhaust fan on the wall above the toilet, it doesn't seem to have much pressure in terms of sucking out air, but if you place a sheet of tissue over it, it'll stay on the vent grate..... so I'm not sure if I have a vent pipe at all, let alone if it can be clogged somewhere. Though, in my house we had that happen to an old w/d vent pipe, and it wreaked havoc on the plumbing, so I'm pretty sure it's not that either, but again, I'm no expert. I'll try pouring some water into the w/d line just in case the trap is dry (sounds like I'm competent though, right? lol), but I'm pretty sure it's always been dry. Oh, btw, the toilet is NOT affixed to the floor, it moves a bit, but the smell is also IN the water, you can smell it showering, or when the toilet is just sitting and hasn't been flushed. The smell is usually on hot days, but honestly, I think we get used to it when we're home, and it seems much worse when we leave and return. I've read tons of forums that suggest the septic/sewer may be the problem, or the well water might me funky, but I'd like some expert advice as the park just says call a plumber, and my house is new (6 mths old) so I really doubt that my pipes are the problem.

I live in a brand new park model rv, with rv plumbing I suppose ( it's more exposed, not like a stick built ), and NO holding tanks, just regular black pipes to the sewer line. I've recently been smelling the coming from the toilet presumably, and also in the shower water. The park uses well and city water. They had plumbers out to clear the mainline maybe a month or 2 ago. I know this because they had a giant snake like a water hose reel....and my toilet was gurgling prior to them snaking the main line. The park is old, like really old, pre-1950's if I had to guess. l have a w/d hook up that has never been used, the contractor said it had a leak that needed repair (another issue for another day). I recently went to a plumbing store and the guy gave me a valve and hose to connect to the hot water line so that I could connect my dishwasher. The is no vent for it up top on the sink, nor is there a loop in the drain line, not sure if it matters, but I'm trying to give as much info as possible

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