There are a few possibilities here, so let's start with the most obvious:
(1) Make sure your system is on and your pump is running.
(2) Make sure your pump is "primed" (this means if you look at the portion of your pump that has a clear plastic or glass removable lid above the pump basket - you can see water churning around and the water reaches the surface of the lid). If your pump isn't priming - this is likely where your issue begins. If the pump isn't priming, you may need to add water to the area where your pump basket is located by removing the lid. If it is full of water, you want to double check that your water level in the pool is above the skimmer opening and that your pool isn't taking on air where it should be filled with water.
Generally speaking, the above mentioned issues will be the culprit. However, if all of those are checked or tested and appear to be working, then you want to make sure that you don't simply have a faulty pressure gauge. You can get a new one for less than $10 at most local supply stores (and you can return it if that isn't the issue).
The more serious cause may be related to debris in your pool. If you've had a lot of debris recently in the pump basket, then you have debris getting past your skimmer baskets. You may have a clog in your skimmer line somewhere. You may also have an issue where debris has made it past your pump basket to clog or even break your impeller. If you aren't handly, you'll want to consult a professional before taking your pump apart to get to the impeller.
No matter what, a filter pressure reading of 0 means you aren't getting water to your filter...not that something is wrong with your filter (beyond maybe the pressure gauge). HIGH pressure means your filter needs attention (usually cleaning or backwashing depending on the type of filter you have). When the pressure is 0, that means that somewhere between your skimmer and your pump there is a problem that is restricting water flow into your filter.
If you live in the greater Dallas area and need help with these items or something else related to swimming pools, please visit http://www.ABetterPoolService.com for helpful information and friendly answers to your questions. If you are outside the Dallas area, we'll still be glad to try to help over the phone at no cost to you and maybe even point you in the right direction of a service firm in your area if you need one. You can find our phone number on our web site.
This answer isn't meant to be a solicitation, but rather an offer of yet another place for another resource for help if you're in need and not finding all the answers on this forum. Have fun out there and enjoy your swimming pools!
It depends if you mean replacing just the grate or repairing the plumbing. Yes to the grate and NO to the plumbing. The grate is usually attached with 2 screws to a ring set in the plaster.
The standard formula is Diameter x Diameter x Depth x 5.9 for the number of gallons. Assuming the water depth is 4 feet, it's 27 x 27 x 4 x 5.9 = 17,200 gal.
Maybe. There is an exclusion for damage caused by domestic animals in most all homeowner's policies. If a wild animal such as a bear or deer causes the damage some policies may cover the damage. Check in your policy, Section I - Perils Insured Against (is a list of exclusions)
You can rehang the liner on your above-ground pool if it fell over in the winter but you will need to remove the pool corner caps, the rail, and all of the water. You can then re-stretch the pool liner and refill the pool.