Water tank question? Strange occurence

zdunc · **Joined:** 24 Sep 2013 09:20 **Posts:** 393

So, I'm flushing my drinking water system in prep for cruising. My set up has two deck fills instead of the one that over flows to both tanks. I'm filling the large starboard tank from the deck fill with a bleach solution and planning to fill until I see water come from the vent hoses to purge them as well. I think I've identified the vent hoses in the bilge (starboard near the mast and port nearer the bilge?), although I've just always guessed that is what they were (2 open ended water hoses). I fill and fill and never see water come from the vent hoses or from anywhere. Check the closed inspection ports and see water seeping out and tighten down further, more water seeping out starting to make a mess. So, turn water off unsure if vents attached, clogged, something? In the mean time, I decide to go ahead and charge the system with the bleach solution. Leave water running at faucets for 10 minutes or so and then notice I can still see water bubbling around the closed inspection ports. How can that be, I think? Should be going down. Look again and tank is concave!! Suction is pulling the top of the tank down with the water level. Can't open the ports due to all the pressure. So, turn off water, and very slowly the pressure starts to release with some bubbling below. Don't think I broke anything but confused? This ever happened to anyone before? What about the non vent part?

cseltzjr · **Joined:** 16 May 2009 08:06 **Posts:** 236

I can't offer any explanation to what you have happening but...we have never used the deck fills to fill the water tanks and none of the T-37 owners I have sailed with do either. We take the hose down below and fill the tanks directly through the ports in the top. FWIW

jvoelxen · **Joined:** 21 Oct 2006 15:36 **Posts:** 268

Seems like your tank vents are blocked. As you draw down a tank you're drawing a vacuum. Will only happen if the tank is not vented.

zdunc · **Joined:** 24 Sep 2013 09:20 **Posts:** 393

Hey C, yeah, that's how I have always done it too. Decided to do a "super" flush, thinking it was possible that 30 years of gunk in the deck fill hoses could somehow make it's way to the tanks with a full system and wave action. No idea if it could, but I'll tell you, there was a ton of gunk and trash that came through. I had to flush and shop vac about 50 times before all the sediment was gone. May have been easier to just buy new hoses although the one to the starboard tank looks like it might be tough to snake it through, and I think the access to the fittings on the tanks might be limited. Guess I'm glad I got it out, but will probably go back to filling down below.

J, that was the conclusion I came to as well. On the whole my system is clean and works perfectly. This one is a head scratcher. Guess I'll dig into it a little and see if I can find what is up.

puffcard · **Posted:** 28 Sep 2016 08:47

I'll check today to see where our vents are. isn't there a vent line loop in the port settee locker just forward of the nav station. They are higher than the inspection ports, so could put pressure on ports. We fill from the deck fills, I don't fill from the tank inspection ports very often. Only at the start of the season, when cleaning tanks. Once you start cruising, you'll be filling from jerry jugs most of the time and you don't want to be dragging them below. If you get a lot a of dirt in the water tanks, check the deck fill o-rings, bet they are missing. Also check the diesel fill, water and dirt in that tank causes big problem. On the o-ring seals at deck and tank top, clean them and lubricate them with SuperLube Teflon clear lube https://www.amazon.com/Super-Lube-21030-Synthetic-Grease/dp/B000XBH9HI, a must have on the boat. Use on all o-rings, head, sink facet, any rubber parts and while rebuilding pumps. It's also food grade, safe for food contact. Bleach only use the name brand Clorox, and use it VERY sparely. Super corrosive, plays hell on rubber and metal parts, and NEVER use in head. Never more than a 1/4 cup in stbd tank and less in port.

cseltzjr · **Joined:** 16 May 2009 08:06 **Posts:** 236

The starboard tank vent is routed through the aft hanging locker on the starboard side. The port side tank vent is in the port locker just forward of the nav station. The boat's original manual says that these are open ended "vented loops". However, there is no vent at the top of the loop and both hoses disappear back down into the bilge. Almost as if they were connected together? However then, there would be no venting (one tank to the other). It would seem strange to me that they would put the open end in the bilge except that way if the vent ever did end up putting out water (over fill or heeled over very hard) it would go into the bilge instead of the locker. I have never had a problem with the water fill but your situation does dictate that you have it up and working properly. If the condition of my vent hoses is any indication of the condition of yours (all sticky with plasticizer) they are probably also a mess on the inside.

jvoelxen · **Joined:** 21 Oct 2006 15:36 **Posts:** 268

Just to add to what has been said above. The tank vents are loops located in the lockers described above. The tops of the loopson the are about 3 to 4 feet above the tops of the tanks. The deck fills are about a foot higher than the top of the loops. If you fill the tanks from the deck fills, you have to just about over flow the deck fill to overflow through the vent. When they do overflow, they will discharge to bilge if not blocked.

Now in this deck fill over flow condition, you'll have at least a 4 ft column of water pressuring the tank (about 2 psi). I used to be lazy and fill my tanks by dropping a hose in the deck fill and wait for the overflow. Unfortunately, I literally blew up my stbd tank with the over pressure. The stbd tank is particularly vulnerable because it's long and flat so the upward force is enormous. Because of my experience, now I always fill my tanks down below thru the inspection ports.

zdunc · **Joined:** 24 Sep 2013 09:20 **Posts:** 393

Thanks for all the responses. I got new o rings a few weeks ago, and I'm sure the old ones weren't doing the job. Definitely use Super Lube too. So, I found the vent loops as described, removed the hose clamps and hoses and blew through them. I got a little resistance going back into that starboard tank, but then it cleared right up. Couldn't see anything floating in the tank. Who knows? Maybe an air bubble or something? I repeated on the port side just to be safe. All clear there both directions too. So, it seems to be all fixed now. J, good info on how much would need to fill to get the vents to discharge and also the problems with that. Definitely will keep that in mind.

Velera · **Joined:** 29 Dec 2006 09:38 **Posts:** 656

I disconnected my deck fills from the tanks and put a cap on the tank hose opening some years ago as I found they just were a problem to keep clean and it is much easier not to over fill the tanks if you do it from the salon fills. Just replaced the O rings. Interestingly, the Kracor folks did not have the 3.5" O rings in stock. Kept saying they were 2.5 inches.

Ray Durkee
Velera
T37 #373

Tartan37.com

Water tank question? Strange occurence

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