What is it?

[Viper]

Tom, you are correct in that the unit will do its job no matter what position it's in but in our area, if it's not upright to allow for complete draining during winterizing, it won't make it through the winter. In a horizontal position, there's also no guaranty that antifreeze or air will displace all the water in the tank.

[Midnightsun]

Here is an excellent video explaining what an accumulator does.

[bud37]

My unsolicited advice.... .... would be to remove that from the boat, then and if it comes that you need one, get one of the small marine ones. That will remove all doubt and wonder as to what is the state and safety of that thing......good luck folks.

[Grafunkus]

Source of the post Here is an excellent video explaining what an accumulator does.

Thanks for the video.

[Midnightsun]

Looks like this is your unit. http://www.seaflo.com/en-us/product/detail/3196.html

It is a marine unit by the way and the bladder pressure needs to be rechecked at least every year for proper pressure. Just like the tires on your car, rubber is not air tight and does allow air to pass decreasing the pressure with time eventually rendering the unit useless if the pressure is not topped off regularly. Best time would be pre-launch every season. Your unit is most likely 8 litres which is at least 5 times the little plastic ones which all seem to be around 0.75L

Here is a link to a few at Defender. https://www.defender.com/search.html?q=accumulator

[Viper]

I could be wrong but I don't think it's a Seaflo. It's a common design used by several manufacturers though. Personally I'm not crazy about the tiny tanks, I suppose they're okay for minimizing pulsing and using a single faucet but open a couple at the same time and suddenly the advantage of minimizing pump operation is out the window.