Algae in Fresh water tank!!!

So as a first timer on a budget I purchased a 22' 1999 Tioga. It is in decent condition but has not been used much recently thus I have been going through and cleaning, replacing or updating each part or system as needed. One of the things that has me vexed is the fresh water tank. It had a bit of algae build up in the tank so I bleached out the tank using the .25 cups per 15 gallons of water rule. It killed all of the algae however i think the biomass (dead algae) has clogged a screen or filter inside the water tank.  I am assuming this because when I removed the connections to the tank when full, water would not drain out. You might ask, did you use the drain valve. Well it seems that in my model there is only one outlet that leaves the freshwater tank and it "T"s off to either the drain valve or the water pump. I couldn't figure out whey my water pump was running in-consistently even with a full tank of water, until i back-washed the water line heading into the pump and the system worked fine for a bit until it seems there was a new blockage requiring another backwash.  My question is, is there a product or way to remove the algae with out replacing the tank or cutting a hole in it?  Any thoughts or wisdom is greatly appreciated.

Run a wire up the tube into the tank and break open the screen if there is one.  Then add a screen like this one:  https://www.amazon.com/SHURFLO-255-313-Twist-Pipe-Strainer/dp/B000V2W0GE/ref=sr_1_2?ie=UTF8&qid=1523016739&sr=8-2&keywords=rv+water+pump+strainer between the tank and the pump. 

Welcome to the forum.
I don't believe there is a screen at the outlet of the tank unless it's in the line like similar to the one mentioned by Al.  I think I would drop the tank, cut a good size hole in the top, clean the tank of any sediment then manufacture a bolt on cover.

Before I cut anything I?d add a double dose of Rid-X to the tank and take the rig for a half hour drive, then let it sit for a couple days. There?s a good chance the enzymes will breakdown the algae. Then if you truly don?t have any low point drains, disconnect the pump from the tank and connect a hose to drain the tank.

Before I cut anything I?d add a double dose of Rid-X to the tank

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NO!!!!  Rid-X is not intended for use in potable water systems!!!!  It is for septic tank waste water only!

I don't know that it is actually poisonous, but the MSDS for Rid-X says NO.

Agree with Rene that a screen on the tank outlet is highly unlikely, but in many RVs the water pump has a screen at its inlet.  And it is also possible for a clump of dead algae to clog a valve.

First investigate the water pump to see if there is a disc-shaped gadget or a bowl at the inlet. If so, that contains a screen. It usually has a screw-on or snap on access.

For the outlet valve, open the valve and then run a wire up the drain hose.  A length of 14 or 12 gauge wire is usually a reasonable combination of flexibility and stiffness to poke through a clog.  Or, backwash with low pressure. Repeat and gradually the accumulated sediment should work its way out.

Maybe a gallon or so of straight vinegar?

So I looked at the 1999 Fleetwood Tioga Owners manual (available at website below) and it states there is a removable screen filter upstream of the water pump.  Page 4-3..

https://www.fleetwoodrv.com/rv-owners-manuals

Gary RV_Wizard said:

Agree with Rene that a screen on the tank outlet is highly unlikely, but in many RVs the water pump has a screen at its inlet.  And it is also possible for a clump of dead algae to clog a valve.

First investigate the water pump to see if there is a disc-shaped gadget or a bowl at the inlet. If so, that contains a screen. It usually has a screw-on or snap on access.

For the outlet valve, open the valve and then run a wire up the drain hose.  A length of 14 or 12 gauge wire is usually a reasonable combination of flexibility and stiffness to poke through a clog.  Or, backwash with low pressure. Repeat and gradually the accumulated sediment should work its way out.

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Thank you everyone for taking your time to assist and troubleshoot with me. I agree that a screen on the tank is highly unlikely but is my current working theory. There is a screen inline filter right before the water pump, I have taken this off and cleaned it multiple times. However I have determined this to not be the cause of the blockage. I have a separate pump that I directly hooked up to the water tank outlet without the inline screen filter and encountered the same issues. I have also replaced all of the tubing outside of the tank that lead to the drain valve and the to the pump. the only place I have not replaced or checked is the inside of the tank as I cannot reach into it or see into it. I have even removed the the "T" connector that screws directly into the tank, with a full water tank and still no water comes out, this is baffling me.  I will add pictures if it will help.

kdbgoat said:

Maybe a gallon or so of straight vinegar?

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I have thought about this idea as well, I wasn't sure that vinegar would dissolve or break apart the Algae. I am wondering if i am left to driving it around until it breaks up on its own over time.  I think that is my next step before I poke holes in any screens.

You say you removed the "T". Did you try and stick a piece of wire like a coat hanger in the hole and see what you feel. Is it hard or soft? Put a hook on the end and try to fish something out.

Rene T said:

You say you removed the "T". Did you try and stick a piece of wire like a coat hanger in the hole and see what you feel. Is it hard or soft? Put a hook on the end and try to fish something out.

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I did put a wire up into the opening. It felt hard and i didn't want to damage a screen or any other part that may be on the inside of the tank that I was unaware of existing. I will try again this weekend.

Where you said it felt hard, I would think that it's not algae. Keep in mind there's water behind whatever is there and it may take some pressure to move it. Use a piece of pipe which just barely fits in the hole that way the water will have a way to escape through the pipe. Once the tank is empty, maybe you can go down through the gravity fill port with a scope and try to find the item.
If it is solid, I think you have no choice but to drop the tank as I said earlier.

This may work if dropping the tank is not a option:
If there is a foreign object in there, maybe you can get around it. Find a thin wall piece of pipe, metal, pvc or some tygon tubing. You want it to be as tight as possible and the thinnest wall you can find. Make it about 6" long. Before inserting it in the fitting, drill a whole bunch of holes around the OD of whatever you use. The foreign object then will not be able to plug up the pipe and hopefully you'll still have enough water supplied for the pump to work as it should.

I'm no RV expert, but can you get a shop vac on the hose fitting?  Or in a main filler valve on the top of the tank, if there is one?  Maybe even to blow air into the tank?

Algae can only grow if there is sunlight.  Keep the light away, and no algae.

Or go to the fish shop and buy a few Plecostomus to put in there.

One obscure problem that I've seen reported a few times is a tank blockage caused by a piece of the tank wall plastic.  When the holes are cut in the tank to connect water lines using a "hole saw", the resulting disk of plastic may fall into the tank and remain there. Eventually it gets sucked to an inlet or outlet and blocks it. It may move around when driving, so the problem can come & go.

Gary RV_Wizard said:

One obscure problem that I've seen reported a few times is a tank blockage caused by a piece of the tank wall plastic.  When the holes are cut in the tank to connect water lines using a "hole saw", the resulting disk of plastic may fall into the tank and remain there. Eventually it gets sucked to an inlet or outlet and blocks it. It may move around when driving, so the problem can come & go.

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This is an interesting thought and would produce the symptoms that I seem to be encountering. I will continue to work on it this weekend and will report what I find.

Gary RV_Wizard said:

One obscure problem that I've seen reported a few times is a tank blockage caused by a piece of the tank wall plastic.  When the holes are cut in the tank to connect water lines using a "hole saw", the resulting disk of plastic may fall into the tank and remain there. Eventually it gets sucked to an inlet or outlet and blocks it. It may move around when driving, so the problem can come & go.

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That is what I was thinking too.  From what I have seen on my first RV, a Keystone Alpine, which is one of keystone's 'luxury' models, thee workmanship is very crude...

It could even be a beer bottle top in there.

So, I wasn't able to get to the water tank until today. This week I purchased a small scope camera that connects to your phone. They are surprisingly inexpensive and easy to use.  It is small enough that I could look inside the tank opening. Upon doing so I found a screen insert that fit into the tank opening that ran to the water pump. . I was able to pop it out and water came running out of the tank. All I have to do now is flush the tank a couple of times to get all of the dead algae out.  I will not be putting it back in as I have a filter right before the water pump.

Thanks to everyone for their advice and thoughts.

Imbabura said:

................... This week I purchased a small scope camera that connects to your phone. They are surprisingly inexpensive and easy to use.  It is small enough that I could look inside the tank opening. ...........................

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I purchased one of these also!  Depstech brand (https://www.amazon.com/Depstech-Semi-rigid-Inspection-Megapixels-Waterproof/dp/B06WRNGYXY/ref=sr_1_cc_4?s=aps&ie=UTF8&qid=1523884093&sr=1-4-catcorr&keywords=depstech)

There are others out there, this one is for android only.  I got it as a Christmas one-hour deal for $12 and have been using it for plumbing issues ever since.  Handy to have and we all have cell-phone anyway..