How to stop air getting into water tank

[epatant]

I pass a hose down the filler until it reaches the bottom of the bladder a couple of times a year and let the water run out for about 10 mins . It helps purge the tank and lines.

[Franziska]

Use a y fitting instead of the t fitting close to the tanks end of the filler. It reduces the risk of getting an unwanted U shape.

[OS2Dude]

I've never used a bladder tank, so take this for what it is worth.

I would think a top fill with a smaller supply hose should let any air displaced by the filling water out. You should not get air into the tank once filled. The tanks (as I understand them) are designed to collapse by outside air pressure/gravity as the contents exit. How is the tank secured? There is nothing preventing the top/sides of the tank from fulling collapsing in place? If the tank can not collapse air will be drawn into the tank to replace the lost volume of water. Do you hear any gurgling sounds?

Why do you have to empty and manually massage the tank to remove air? Once the fill port is open it is one giant vent, unless something is acting as a seal. Even a seemingly shallow sag in the fill line can act as a P trap and cause issues. (Ask me about a shallow sag in the black water vent line when we bought our boat... )

[JPA Cate]

If you add a vent to a bladder tank, if the boat is ever upside down, all the water will try to drain out from the vent line.

We had Vetus bladders in our first Insatiable, and there was an inlet and an outlet, and no vent line. Worked well for many years, but eventually both failed. First replaced by other bladders which failed in 2 and 3 weeks respectively, and then with s/s tanks we had made in NZ, which were in use when we sold that boat.

NO Vent line is necessary. Replace any O ring seals with new ones, lubed with silicone grease. Should not suck any air in. ...n.b., Jim uses vacuum pump grease for that.

Ann

[HopCar]

Originally Posted by hd002e

How does one go about doing that? Do I have to make another hole in the bladder?

Add a vent. Yes you have to cut a new hole in the tank. It’s not hard. Getting the inner flange through the hole can be a struggle but it is doable.

This is the fitting you need.
https://www.imtra.com/4387bc6a-82f5-...nks-detail.htm

[HopCar]

When you get tired of messing with the bladder tank, order a plastic tank from Ronco. Avoid aluminum tanks. Stainless is ok but plastic is cheaper and will outlast the boat.
https://ronco-plastics.com/