Disclaimer: The following repair guide is provided for informational purposes. Not all these repairs have actually been tested here. iSoaker.com and its affiliates cannot and will not take any responsibility to any damages caused as a direct or indirect result of anything attempted. Use at your own risk/discretion.
Blasters belonging to the pressurized reservoir tech category include the SS50, XP20, SC400 and XXP175. Water is put under pressure by pumping air directly into the reservoir. One of the main drawbacks to this type of design is that it often takes quite a few pumps to pressurize the reservoir. Also, it takes even more pumps to maintain pressure at later stages. The following are some problems sometimes found with this class of weaponry.
Pumping is difficult/impossibleIf the pump cannot be pushed or pulled (if applicable), its innards may have dried out and crusted. Try filling the reservoir with water and pulling/pushing harder on the pump. If it breaks, the blaster was useless anyhow.
If pumping is merely difficult, addition of some form of lubricant (i.e. Vaseline) to the pump shaft may help alleviate this problem.
Opting to open the weapon for a pumping problem usually does not help as the pump's shaft is typically sealed inside.
Pumping does not pressurize the blasterEnsure the reservoir or reservoir cap is securely attached to prevent air/water escaping from where it should not.
Check the O-ring around the cap or part where reservoir attaches. If there is damage to this ring allowing air to escape, it must be replaced for the blaster to work. One may be able to find a replacement O-ring at a local hardware store.
Blaster will not shootMake sure there is water in the reservoir and that the reservoir is adequately pressurized. Try pulling the trigger harder.
Check the nozzle to make sure it is free of debris. If there is debris, attempt to clear the blockage by using a long needle/wire but be careful not the damage the nozzles or any of the blaster's inner-workings.
If using a blaster with multiple nozzle settings, ensure that the nozzle selector is properly aligned to the nozzle of choice and not in-between settings.
Blaster shoots mistOn some models, ensure the blaster is in an upright/horizontal position such that the output tubes are immersed in water.
Blaster continually shoots as soon as it is pressurizedOlder pressurized reservoir models control their water exiting the nozzle by a mechanism which pinches the soft, plastic tubing inside the blaster. At times, however, this mechanism loses its strength and is no longer able to pinch the tube properly, resulting in the continuous stream. The only remedy in this case is to open the blaster and look for the tube pinching device. It may need to be assisted in closing the tube when the trigger is not in use by attaching rubber bands to it. This, however, does not always work effectively and it may be in one's better interest to simply retire that blaster and purchase a newer, better built blaster.
Newer models have an enclosed plastic valve system which cannot be opened. However, sometimes the problem here is that the pistons on the valve that the trigger tugs on have become dirty. Removing dirt from the pistons and adding on a little lubricating oil can often help this problem immensely.