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Old 01-05-2008, 03:25 PM   #1
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Gray water tank repair

Need some help. The gray water tank (shower drain) on our Present 42 was built in place between the stringers. Over time- the top of this tank has delaminated (the plywood should have been covered with FG beneath) and I need to correct this. Upon inspection today- the bottom has some soft areas also.
Can I vacuum/ dry this area after removing the remaining top and rebuild this tank? I reworked the transom on a 21' cuddy I had years ago and remember using Roven Woving, resin and another typy of FG material. What would the process be?? Thanks to all in advance.
Steve
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Old 01-05-2008, 05:12 PM   #2
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Gray water tank repair

Mr. Forklift. Is it possible to remove the top of the tank and put a smaller container in that space with a float and bilge pump to handle the shower water?
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Old 01-05-2008, 09:37 PM   #3
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RE: Gray water tank repair

Yes it is- and this was my first plan. However- I think that I would rather work with the existing tank to simplify the plumbing needs. This tank has a float switch and pump- also two inlets from both heads.

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Old 01-06-2008, 09:43 AM   #4
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RE: Gray water tank repair

That sounds like what a number of us have. These boats appear to have been designed to just let the bilge pump take all the sink and shower water out. However most of us don't like the idea of soap, hair, and whatever else floating around in the bilge, so we have smaller containers with a pump and float switch to automatically take care of those waters.

Over time that glass covered plywood box was bound to leak. It sounds, from your post that the box might actually be glassed into the stringers, so we don't want to think about replacing it, just replace the top and repair the bottom. A new plywood top could be fabricated and sealed with fiberglass again. If I was doing it I would put a couple of coats of penetrating epoxy on the plywood first and then a couple layers of fiberglass cloth. Real easy to work with.

I would use epoxy resin rather than polyester. A little more expensive but in the quantity needed, (1 quart of resin should do all this repair) not a bank breaker. Cut and fit the new plywood top with a 1/4 inch or so extra gap on each side. Then spread the resin on the plywood, lay the cloth on and wet out the cloth well. Cut the cloth with a pair of cheap throwaway scissors so you can wrap the plywood just like wrapping a present. While this lid isn't going to get much abuse, wrapping this way gives good strength to the edges and corners. Make sure you wet the cloth all the way through. Squish and wiggle the epoxy all through the weave.

After it's dry you can sand any rough spots smooth. A coat of paint will give a nice finished look. If you need to drill holes to hold the lid down drill them oversize prior to glassing. Then the epoxy resin will get in the holes and seal the plywood. Re drill the holes the proper size afterward and you should not have bare plywood showing.

Replacing the bottom of the tank is probably more work than it's worth. If it just has some soft areas but is for the most part sound, then you just need to re-waterproof it. That should be done with epoxy resin and cloth also. You might get by with just penetrating epoxy and some resin, but since you should be making a new top with the same items it's just a little more time to do it right.

Dry. Make sure it's dry. Vacuum any water out, put a hair dryer in and let it run (with proper monitoring, on low heat) for a couple of hours. Or if time permits, a couple of weeks with good ventilation. After you are sure it's dry, and only after it is totally dry, begin the repair.

I'd start with a couple of coats of penetrating epoxy. Then follow up with a couple of layers of cloth and epoxy resin using the same techniques as you used on the top. Doing the top first in relative comfort will give you the experience you need when working bent over in the bilge. Same gift wrapping style to extend at least 4-5 inches above the bottom of the box. We don't care too much about looks inside the box because it's just not generally part of a boat tour when friends come aboard. We're more interested in making sure it's watertight. 2 well wetted layers of glass cloth will work well. Let that epoxy set and you're ready to put the pump and switch back in and secure the lid.

If you have an industrial supply store for fiberglass supplies that will be your cheapest source. West Marine or any of those stores also sell the same supplies at a significant markup.

Another thought just crossed my mind also. Did the bottom go bad from the water inside the box/tank or outside? That is, is the box so low in the bilge that the bilge water is helping to rot the wood? Those of us in salt water don't worry too much, but if you're in fresh water that can help cause a problem. If that is the case, then eventually you're in the replacement mode. To delay the replacement I might add a couple more layers of cloth inside making a stronger box, not depending on the plywood bottom for support.

The really good solution to this is a Poly tank with a large screw out access plate in the top. This allows you to put your pump and switch inside and do the annual degunking. With a poly tank you can have them spin in ports wherever you like and in the size that fits your hoses.

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Old 01-06-2008, 09:47 AM   #5
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Gray water tank repair

One more thing I forgot. If you are painting the new epoxy coated areas, wash it well with soap and water to get rid of the amine blush that will be on the surface. Paint won't stick unless you wash it well.

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Old 01-06-2008, 10:26 AM   #6
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Gray water tank repair

If you're going to use epoxy and cloth, the cloth must be epoxy compatible. You can use polyester with any type of cloth but you must buy epoxy cloth for epoxy. Something to do with the coating on the cloth.
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Old 01-07-2008, 08:18 PM   #7
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RE: Gray water tank repair

Thanks to all-- This is the info I was looking for. This project could be a test for a later project. See my next post

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Old 01-09-2008, 12:13 AM   #8
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Gray water tank repair

Let us know how things go and shout if you run into a problem.

Ken
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Old 02-08-2009, 08:13 PM   #9
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RE: Gray water tank repair

Ken,This project is about to come due. I have cut most of the old tank out with a Sawzall and I think I still want to build a new tank in place like we discussed. What kind of coth do I need to work with? I remember "Woven Roving", etc. from a project A few years ago but don't remember what type material to use where. Any advice?
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Old 02-22-2009, 04:55 PM   #10
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RE: Gray water tank repair

Ok, I re-read my other posts and we were talking about repairing the old tank. It sounds like now, if you've cut out most of the old one that you want to build a new tank and put it in?

If so, I'd plan on making an entirely fiberglass tank with no wood to go bad. It's a little more work, but you'll have no worries for the next 30 years. Measure exactly how big you want the finished box and then make a male mold (box) a little smaller. Screw a flat board/plywood on the open end of the box which sticks out at least an inch in all directions. This is your flange for the lid. For my project I'd round the corners well. If you want the box to "hang" on the stringers then you'll need to lay up the flange with more mat and cloth for strength. If you want the box to fit totally in between, then measure and build accordingly.

Sand and finish your mold to a nice smooth finish and seal with a couple coats of sealer. The smoother this is, the smoother the inside of your tank will be, which means easy cleaning. After your finish is dry and hard, wax it. Then wax it again. This will keep the resin from sticking to the mold.

Get your resin, glass mat and glass cloth at the local fiberglass supply house. Tell them what your project is and they will get you the correct stuff that will all work together. The basic idea is that the cloth is easy to make smooth and the mat gives good strength. The resin binds it all together. Listen carefully when they explain about making sure the mat is thoroughly saturated with resin.

Lay up your box using the instructions that come with your resin. The edges of the box flange will normally be something less than square and flat while you are soaking the resin in and laying the cloth on. No worries. Let the cloth extend slightly further than the finished flange will be. As the resin sets it will get firm to the touch. Now's the time to take a SHARP razor knife and a straight edge and trim the edges like you want them. The resin will also be a little tacky so use a scrap of plywood you will throw away as the straightedge.

When set, unmold it and decide where your inlets and outlets need to be. This would be a great place to get real fancy and use bulkhead fittings and all that cool stuff. I wouldn't be so fancy. Depending on your particular setup, I might just use a plastic thruhull in the lid or the side of the box for the shower to drain in, and let my pump hose go straight thru the lid and to the thruhull overboard. I think I'd have my electrical wires do the same thing, properly protected from chafing but nothing fancy and straight thru the lid. My thought is that if/when I needed to work on the system I could lift the lid and all the pieces would come out and set in the bilge. Or if the hose/wires were long enough, up on the cabin sole where I could actually work on it. Charles idea of mounting the switch and pump on something is a good one. Depending on which pump/switch combo you decide to use you'll need to field engineer that part.

For the top, I'd simply make a flat lid. This can be laid up on any no stick surface with the same resin/cloth/mat that the box is made of. An old piece of formica countertop works fine. Wax, then lay out what you need size wise. Something that might work for you, is marking the size lines directly on the formica or waxed finished plywood so you know that everything is within the boundaries. This can again be cut to size as above before the resin is totally hard.

I'd make "pins" to permanently attach to the lid for keeping it in place. I'd probably buy two or three 1/4" stainless bolts long enough to have about 3/4" of non threaded shoulder. I'd saw off the threads keeping the smooth shoulder area about 3/4 inch below the head. Then I'd grind them to a nice taper and round the end. I'd clamp the lid on the box and drill holes thru the lid and flange in three places that will be easy to see when the box is installed. Like maybe the middle of each end and the middle of the front. Take the lid off and drop the bolts thru the lid from the top. Glue them in place with more epoxy. Now the lid is fairly secure from being dislodged, easy to remove when needed, and easy to get back on in the right place each time.

Wash everything real well with soap and water, then paint with your favorite bilge color to make it look factory fresh.

I think that's the info you wanted. If not, just ask. I appologize for the delay in getting back to you. I seldom look down too far on the list.

Ken
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Old 02-22-2009, 08:38 PM   #11
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RE: Gray water tank repair

Ken,
*This is great info- just what I was looking for. Thanks for taking time to write it all out for me.

Steve
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