<emTank<src=”http://https://i.postimg.cc/85Rw0nk8/IMG-20200110-131020.jpg&#8221; alt=”water tank” />

Right, I have this tank on our motor home, sorry about sub standard sketch.
The problem is that the overflow pipe on left is too low so when I fill tank and fill it right to top it starts to syphon out and drain tank to around 60%.
Now this tank is buried deep in the motor home and all I can easily get to is the bottom 3/4 of the overflow pipe and the inspection cap on the right. Ideally I would like to just cut off overflow pipe internally but that’s not possible as inspection hole is too small.
So can I do something with the overflow pipe externally??
Thanks in advance
Simon

Bear with me just trying to post image

(https://postimg.cc/R60c3dnG)" alt="tank" />

Here.

Can’t see the image cause blocked at work but can you fit a breather to the highest point of the overflow pipe to stop the ability to create a siphon?

I imagine even fitting the breather to the highest point you can access would help massively. I would have the breather as something like a pipe going as high in the van as possible, definitely at least 30cm above the highest point of the tank (going upwards without any downhill bits as they’ll just siphon like your existing pipe.

stick another smaller vessel on the end of the overflow pipe, and have an outlet from that high enough to stop the syphon starting.

Can you lift the whole pipe assembly upwards?

I’ve got to wonder though, presumably it’s designed like that for a reason?

Thanks Cougar.
I was thinking that Olive , would I get away with a hole in pipe. The top part of the pipe is hidden but if I put a hole as high up as possible could that work ??

A hole would probably allow backwards contamination assuming that’s your drinking water. Also that hole would allow water out in some conditions too I’d imagine. As for breaking the suction you could try a hole first

Yes, drilling a hole as high in the pipe as possible will stop it siphoning.

How did you post my pic Cougar ??

Couple of ideas to think of , will start with lifting pipe and see what that does.
Thanks guys

Can you access any part of the tank to put a new breather in near the top, some fill caps have provision for the breather hose so you just run it back up the fill pipe. You would then cap off the drain in a way that it could still ‘blow off’ if using a pressure fill system that can’t overflow through the fill point.

The siphoning is also a big problem with wide flat tanks put under motorhome floors as they can siphon out through the breather when ever the water level moves (turning, braking, accelerating) even if the pipe does not extend into the tank.

presumably it’s designed like that for a reason?

Laziness or ineptitude – take your pick.

How did you post my pic Cougar ??

Copied the URL starting from https and ending at jpg, pasted it into the IMG box.