[egstasea]

Not directly related to tank replacement, but rather avoiding it.

I have an 2002 40 express which I bought used 8 years ago. I had an "oil canning" sound coming from the waste tank when I would pump out. Having read about folks having to replace that tanks, I figured this was a contributing factor. I figured the waste volume was exiting faster that the air volume can get in. I did two things to resolve this, I religiously change the vent filter, so it imposes the least restriction. I also rigged a tee between the vent filter and the tank. On the bottom leg of the tee I ran a garden type hose to a full port quarter turn hose shut off which is zip tied to the engine room ladder. Before I pump out I open the shut off so the tank has another source of air to displace the waste being removed. So far, no oil canning during pump out.

I hope this helps to avoid the hassle you folks have gone through.