Holding tank, gravity feed

[Mumby]

Hi,
Size holding tank for four people?
Ok to build out of polyester resin?
It will be gravity feed. Can anyone suggest a link to information on the plumbing, venting required and best construction technique
Maybe getting a custom plastic tank made is more cost effective?
Cheers

[rwidman]

Buy this book:

https://www.amazon.com/New-Get-Rid-B...s%2C175&sr=8-2

Read it over and over until you understand it.

And buy a purpose built poly tank, don't try to make one yourself. As for size, assuming that this is for a boat, get the largest one that will fit in the space available.