Dirt,
You are exactly right, The water slosh'es out because the thanks are shallow, the vents are on the sides of the tank near the top. As I've said before on other posts, connect all vents together and run the up to the fill port(there's a nipple right beside the fill port designed for the vent).
You can see in Loco's pics below.
I DEFINETLY would not put valve's on the vent lines as other's have suggested.
Loco did a great job of taking pics of his work (repairing the factory error),
I had my dealer repair it the way I wanted and send heartland the bill.
Below is a copy of Loco's post on the water tank repair.
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Here are some pictures of 2007 cyclone repairs I made to the wiring and water tank vents. This is the way it should have been done the first time.I ran 1/2 marine hose from vent to vent with fittings and ran it up to the fill point vent. This way you will fill you tank all the way up with out losing any water. Also some pics of the wiring before and after I fixed the wiring the way it should be. I must note that I have been talking to the factory and they are trying to take care of these things so it will not be like this in the new units. We will see. They better or they will not be in business long! Like I said I love the rig over all. It just needs a little more time
spent on the things under and behind the walls.
Attached Thumbnails//heartlandowners.org/attachment.php?attachmentid=661&stc=1&thumb=1&d=1155520841 //heartlandowners.org/attachment.php?attachmentid=662&stc=1&thumb=1&d=1155520841 //heartlandowners.org/attachment.php?attachmentid=663&stc=1&thumb=1&d=1155520841 //heartlandowners.org/attachment.php?attachmentid=670&stc=1&thumb=1&d=1155523370 //heartlandowners.org/attachment.php?attachmentid=671&stc=1&thumb=1&d=1155523370 //heartlandowners.org/attachment.php?attachmentid=672&stc=1&thumb=1&d=1155523370 //heartlandowners.org/attachment.php?attachmentid=673&stc=1&thumb=1&d=1155523370 //heartlandowners.org/attachment.php?attachmentid=674&stc=1&thumb=1&d=1155523370
//heartlandowners.org/attachment.php?attachmentid=677&stc=1&thumb=1&d=1155523370 //heartlandowners.org/attachment.php?attachmentid=678&stc=1&thumb=1&d=1155523370
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I had to delete some pics of wiring, would only allow 10.