How do you put the mattress all the way down?

The first reason to have a mattress protector is to keep your bed clean. Our bodies are not as clean as we think even though we take bath every day. we perspire at night, our skin produces oil while some of us put on makeup. All this can get into the mattress and once it gets in, we cannot remove it. A mattress protector will not let this happen.
Secondly, we all love to keep our mattress new. we do not want it to shorten the life of the mattress. Dust mites consume dead skin cells and the dead skin cells will remain on your mattress if you do not use a mattress protector.
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When air mattresses first came out, deflating was a major issue. In the last ten years or so, all air mattresses built don't have that problem unless they have a puncture somewhere.

It is essential you get a mattress pad for your waterbed to avoid cracks in the vinyl. Without a mattress pad, natural body oils may break down the vinyl of your mattress causing it to crack.

I have a 5918-505 mI put it togehter for the first time since 1980 I had no problems once I located all of the parts: 4 metal guide rails, 2 wooden ends with 2 wheels in each, 2 wooden drop sides (or front and back that go up and down.) 2 metal toe kick rails that hold the sides up, 1 mattress springs, 4 metal mattress spring supports. attached to the inside of the wooden ends are 4 hanger pieces for the mattress spring support to hang on.

I could supply photos if needed.

See the instructions near the bottom of this web page: (picture at the top of pasted instuctions on th link)

http://www.abcwaterbed.com/pump2.htm

1. IMPORTANT! - Unplug waterbed heater for safety
2. Remove cap and seal and put aside in safe place.
3. Remove any excess air from mattress - slide forearm or broom handle from the head of the bed toward the fill hole to move air pocket
4. Attach the heavy duty hose to the hose valve coupling, connect to the waterbed mattress and other end to the pump intake side. Be sure to include O-rings. Gently push the coupling deep into the mattress.
5. Attach garden hose to the discharge side of the pump, this hose goes to a tub, or a deep sink.
6. Plug in the pump. When it starts it should have a low whirring sound, not a high whiny one. If water is not pumping immediately unplug the motor and check hose connections for tightness, verify there is no air in the mattress.
7. As the pump removes the water, be sure the hose valve coupling at the mattress is pushed down in the mattress to maintain suction. Heavy phone books or other like items will help maintain proper position deep in the mattress.
8. Keep pumping the water out and continuing to maintain the hose valve coupling position low in the mattress so it can keep pumping.
9. Do not leave the pump or the area until finished. A dry pump can burn up.
10. When the mattress is part way empty, you can place pillows under it at the head to help the water run downhill towards the hose valve coupling.
11. Continue pumping until water flow stops or pump changes sound. The more water you get out, the easier your mattress will be to handle.
12. If you are satisfied you have got as much water out as you can, remove the hose valve coupling and quickly replace the mattress seal and screw the cap on.
13. If the mattress is to be stored for a period of time, pour in a large bottle of waterbed conditioner into the mattress before you cap and seal the mattress.
14. We recommend rolling up the mattress from the head to the foot and carefully sliding one end into a wardrobe box. Another wardrobe box can be worked over the top of the mattress. Work one box into the other and seal both ends and tape the boxes together in the middle. You can now safely move the mattress.
15. If you don't get enough water out, the fiber layers can easily slide out of position during moving and you may not be able to get them back into position when you fill the bed.

it is warped, it should be flat, but as long as it's not too bad, it should be ok for use.