Fuel Level Sight Glass Replacement?

My fuel level sight gauges are old and completely opaque, can't see a thing even with back lighting. What is the proper tubing to use to replace them?

You will get lots of suggestions here. When I replaced mine on two tanks I used tubing from West Marine; the same stuff used for water. Although others will criticize my choice, I’m happy to report that after 7 years they are still in service and perfectly clear. Cost was minimal. I do have shut off valves at top and bottom of the tubes which remain closed unless I’m reading the fuel level. BTW, the “proper” tubing is Tigon.

Howard

Tygon perhaps?

RT Firefly said:

Tygon perhaps?

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Perhaps.

hmason said:

You will get lots of suggestions here. When I replaced mine on two tanks I used tubing from West Marine; the same stuff used for water. Although others will criticize my choice, I’m happy to report that after 7 years they are still in service and perfectly clear. Cost was minimal. I do have shut off valves at top and bottom of the tubes which remain closed unless I’m reading the fuel level. BTW, the “proper” tubing is Tigon.

Howard

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I use the same re enforced water pipe for a small tank that feeds the boiler. While mine aren't clear, they can still be read easily enough. Whatever type one uses, it's important to have shut off valves in place top and bottom when not being used to measure tank levels.

Clear PVC is probably fine. Because it is so easy and cheap to replace, its likely not worth doing anything more. Even the "better" alternatives will still melt and spill fuel in a fire situation. But, if you're so inclined...

Below is what I have just installed. (I'm still fabricating the guards and indication markings, so they haven't even seen fuel yet.) Meet up with me in 15-20 years and I'll let you know if it was worth the effort :lol:

Tygon (and Versilon) are brand names that refer to a multitude of different tubing, all with different properties and not all rated for hydrocarbons.

What you want is one of them formulated for what you intend to put in it. I bought mine from McMaster-Carr, about $20 for two 2 FT pieces that made up both my sight gauges. They were one outfit where I could buy a reasonable length (less than a 50 ft roll.) The tubing is specifically rated for use with diesel fuel. Its basically the same clear PVC tubing you can get at a local store, but has a thin inner liner of another clear polymer that has the chemical resistance...In this case FET, which resists a lot of dang stuff.

Here's a pic of the material installed as my stbd side sight gauge (still waiting completion and installation of the guards and markings for level indication.)



Below are the details from the the McMaster-Carr website.
_________________________

Ultra-Chemical-Resistant Versilon PVC Tubing

Formulation: SE-200
Very Flexible
Compatible Tube Fittings: Barbed
Soft (Durometer 65A)
Temperature Range: -30° to 160° F
Formerly known as Tygon, this tubing is lined with FEP (fluorinated ethylene propylene) for better chemical resistance than PVC alone. Tubing is clear, so you can easily monitor flow.
___________________

Here's the part number and cost to ship to me in the PNW.
___________________

David Bowman placed this order.
Line Product Ordered Shipped Balance Price Total
1 6519T14
Ultra-Chemical-Resistant Versilon PVC Tubing 3/8" ID, 9/16" OD, 2 ft. Length 2
Each 2 0 9.64
Each 19.28

Merchandise 19.28
Sales Tax 2.44
Shipping 8.78
Total $30.50
Payment Received 10/12/18 (30.50)
Balance Due $0.00

Thanks for the detailed info. This question was driven by my paranoia about what I don't know will kill me. What I have for gauges now is some sort of tubing with cross hatched reinforcement. I guess fuel line of some sort. Wasn't sure why reinforcement was necessary on this.

RT Firefly said:

Tygon perhaps?

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hmason said:

Perhaps.

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Tygon F-4040-A eBay and Amazon sell various sizes. When we replaced our fuel tanks we used Tygon.

https://www.usplastic.com/catalog/item.aspx?itemid=23487

RT Firefly said:

Tygon perhaps?

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Tygon for sure. It is constructed with a liner that is impervious to fuel. This is true, I replaced mine 10 yrs. ago, still perfectly clear. The PVC tubing I removed was yellowed and nearly opaque. SE-200 is available from McMaster. It's apparently now marketed as Versilon.

Larry M said:

Tygon F-4040-A eBay and Amazon sell various sizes. When we replaced our fuel tanks we used Tygon.

https://www.usplastic.com/catalog/item.aspx?itemid=23487

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Maerin said:

Tygon for sure. It is constructed with a liner that is impervious to fuel. This is true, I replaced mine 10 yrs. ago, still perfectly clear. The PVC tubing I removed was yellowed and nearly opaque. SE-200 is available from McMaster. It's apparently now marketed as Versilon.

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We just replaced our TygonnF-4040-A site tubes after 4 years. It got to the point I couldn’t see through them without a light behind them.

I went with the Versilon SE-200 that Steve recommended. The change over went good with the exception of figuring out how to slip the hose on the hose barb without detaching the lining from the tubing. I ended up using a small tapered plug to slightly enlarge the hose first.

Here’s a before and after. The first 5’ section I ordered was kinked and the lining had separated. McMaster-car overnighted a replacement at no cost. Five feet was $42.57 including tax and shipping.

That looks great. Congrats

Is there a standard size tubing for fuel tanks or a size that is most often seen? I haven't done anything with mine yet and keep forgetting to measure. Would measure before buying but just curious.

bayview said:

That looks great. Congrats

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I owe it all to Steve on Maerin.

firstbase said:

Is there a standard size tubing for fuel tanks or a size that is most often seen? I haven't done anything with mine yet and keep forgetting to measure. Would measure before buying but just curious.

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I don’t think there is a standard. Ours happen to have 1/2” hose barbs. Easy to check though. I just pulled the hose off the upper hose barb and measured. To change out, I opened the lower ball valve and blew the diesel back into the tank and shut the valve. I didn’t spill a drop.

Most tubing will yellow and/or become brittle over time.

I use clear polyurethane tubing for sight gauges.

syjos said:

Most tubing will yellow and/or become brittle over time.

I use clear polyurethane tubing for sight gauges.

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I used clear fish tank tubing 2 years ago. I keep an eye on it but is good so far.

Larry M said:

I don’t think there is a standard. Ours happen to have 1/2” hose barbs. Easy to check though. I just pulled the hose off the upper hose barb and measured. To change out, I opened the lower ball valve and blew the diesel back into the tank and shut the valve. I didn’t spill a drop.

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How did you blow it back into the tank?

firstbase said:

How did you blow it back into the tank?

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With my mouth. I took off the top hose and as i was blowing back, I shut the lower valve off. Our tanks were less than half full. It was like blowing bubbles and very easy

Larry M said:

With my mouth. I took off the top hose and as i was blowing back, I shut the lower valve off. Our tanks were less than half full. It was like blowing bubbles and very easy

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Thanks. I was thinking that given a low level of fuel, gravity, etc. it would be pretty safe to do that.

In the 14 years that I owned my boat I never looked at the sight tubes other than to make sure they weren't leaking.

jleonard said:

In the 14 years that I owned my boat I never looked at the sight tubes other than to make sure they weren't leaking.

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I go with engine/generator hours on a spreadsheet (I use 3.6 gph as an estimate) to see where I am. However, a visual confirmation would be comforting.

jleonard said:

In the 14 years that I owned my boat I never looked at the sight tubes other than to make sure they weren't leaking.

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That begs the question, "Why did you never look at them?"

rgano said:

That begs the question, "Why did you never look at them?"

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He didn’t need the accuracy. Some people have gauges and they never go below 1/4 tank, others go by hours, again never going below a 1/4 tank. I like data. My sight tubes are market in 10 gallon increments. Even though I know my fuel consumption I can verify.

My sight gauges are marked in 5 gallon increments and I look at them once every few days while cruising. I have found that since the sight gauges are mounted at the forward end of the fuel tanks, trim and list will cause reading inaccuracy. My fuel fills are located at the middle of the tanks and I find that taking a dip stick reading is more accurate.

I keep track of fuel usage in a logbook and enter engine hours and calculate remaining fuel. I update the fuel log every 4 hours when I switch tanks. I dip the tanks once a week while cruising and adjust the numbers in the logbook. There is a one to 5 gallon discrepancy between the logbook and dip reading. The dip stick is more accurate.

Some people use engine hrs and a memorable cruise RPM to estimate fuel. Especially when you carry more fuel than you need on a monthly basis of cruising.

Looking at the sight gauge can reveal more information than just how much fuel is in the tank. Water might show up there. With the valves closed after checking a very low tank, opening them after filling will allow a surge into the tube showing possible bottom contaminants. If you don't have a bottom drain, disconnecting the top and bending it over to a container can give you a bottom sample. There may be a few other tricks, but these come to mind for reasons to pay attention to sight gauges.

Emptying and then refilling a tank in known, marked increments is an excellent way to end up with a usage measurement tool. I have a console tank gauge as well as a Floscan installation. It is handy to compare the Floscan to the sight gauge after a day's run at 10 GPH. And the sight gauge is where I would be looking if ever I got into a situation where fuel remaining was a critical issue.

rgano said:

That begs the question, "Why did you never look at them?"

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I found my gage was very accurate. I verified it with a dowel and tape measure soon after I bought the boat.
I could “guestimate” how much fuel I could take on within 10% from reading the gage and knowing tank size.
I asked myself “why would I crawl around in the engine room just to verify fuel level? I already spend enough time in the hole”

I never drained any water or crap from my multi stage filter system. At filter change time the elements always looked pretty good.
I was not in denial I just used those indicators to feel confident in my fuel quality.
Maybe I’m different that way but that’s what and why