water tank 101

[ksmith]

My tartan 27 has a 30 gallon SS under the v-berth. There is a deck mounted fill.

Now the interesting part. Just below the neck of the fill tube is attached a 90 with a hose that runs down to the side of the tank and enters at about the same level as what I would call the primary. There is a hose that runs to the sink (hand pump).

I can not see a vent on the top just a service plate. Is it possible the hose with the 90 should be the vent but the PO has mis-routed.

My limited knowledge says a vent should be at the top and not the side.

[senormechanico]

It's possible that the hose in question goes up nearly to the top of the tank on the inside. If that's the case, when you fill the tank to the top of that hose's end on the inside of the tank it would burp water back at the deckfill connector to tell you it's full.
IMHO the purpose of having this arrangement would be to leave a slight air pocket at the top of the tank for whatever reason. At any rate, you will only be able to fill the tank below that hose's end elevation. To find out, you'll just have to peek inside.

Steve B.

[ksmith]

Thank you good idea. Will try to get a look at it this weekend

[Ex-Calif]

If the cap is vented I would agree with Steve.

Our tank is vented at the tank - terrible idea - when we fill it, and then are heeled over for a while we get a floor full of water. Only 75% of our capacity is useful. I suspect someone changed things on us some time ago.

On your system, if this is the vent, the top is well above any possibility of spilling water while heeled.

Also if the tank fills from the bottom, it has to be vented to let the water in.

The only thing I am curious about is what happens when water enters the top of the stand pipe - maybe there is an inverted J inside at the top with a floating ball valve - like some snorkels, that stops water from entering the stand pipe as you fill.

Curious...