Tank made weird noise and sucking itself out of shape

[ks789]

Odd title, but couldnt think how else to describe it. never had it happen before. was a big job, first clean on a big place etc.but went back to the van when near finished, and theres a weird noise havent heard before, it was the 350 litre tank. not much water left at this stage, maybe 30 llitres, and it had been kind of sucked in out of shape. I quickly pressed the release button on the lid, and a load of air came out, then opened the lid and it went back into shape.

just wonder if this is normal, cant say its done it before. What if I hadnt gone back to the van then? Is this dodgy, or normal and should I keep the lid unscrewed a bit to stop it. 

much obliged for advise.

 

[Jango]

Is you lid vented. Or solid? It does need a vented lid, to stop this happening. Obviously the water was low, so as it’s running out fast it will suck the tank in. It sounds like your lid isn’t vented, if all the air came out when you unscrewed it. 

Some use a solid lid, then drill a small hole in and glue a short piece of hose, into the hole, this would let the air out then

 

[High-tower]

Just the breather got blocked or stuck, just make sure it’s moving freely, and perhaps wedge something in it when you are working to make sure the air can get in to replace the water that’s being pumped out.

 

[ks789]

Just the breather got blocked or stuck, just make sure it’s moving freely, and perhaps wedge something in it when you are working to make sure the air can get in to replace the water that’s being pumped out.

yeh The lid has a little button on it you can press in, but up to now ive never had to press it. Will keep an eye, maybe leave lid off a bit or cut/drill the button out the lid. Ah, i just remembered , there was a leather/vinyl seat cover on top of the lid. This must've stopped the breather. Aha. 

 

[Part Timer]

If the tank isn't vented, airtight, when you use the water in it you're creating a vacuum. Probably because the sides sucked in it opened up the lid very slightly and you heard the air being forcibly sucked in. As the 2 replies above have said, just make sure the lid is vented and it wont happen again.

 

[Jango]

yeh The lid has a little button on it you can press in, but up to now ive never had to press it. Will keep an eye, maybe leave lid off a bit or cut/drill the button out the lid. Ah, i just remembered , there was a leather/vinyl seat cover on top of the lid. This must've stopped the breather. Aha. 

??

 

[P4dstar]

An easy alternative to a vented lid is to drill a small hole in the top and fit a piece of hose, attach it high in the van and it will let air out for you. @Tuffers has this on his tank. Don't imagine he will post a pic of it now as I think he's banned but if you look through his old posts there was one entitled ''FAO P4dstar'' which had pics of his set up.