[Jfhaas]

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.

The oil canning was the exact reason my tank started to leak. Absolutely agree the vent not being changed is the cause.  Also, question wisdom of Tiara using aluminum for the holding tank and the acidity of urine.  When I called Tiara they acted like this was first they heard of this problem. Jack