I have had a continuing problem with algae in the fresh water tank of my 179.  I have bleach cleaned the tank each year in the past, but the problem always comes back.  Last fall I winterized and drained the tank.  To prepare the trailer this spring I inspected the tank with a TV endoscope via the fresh water fill tube and found a major infestation of new algae and that an inch or more of water had remained in the tank since my fall draining.  Clearly the drain is not at the lowest point of the tank so some water and the opportunity of regrowth of the algae remains.

On further inspection I discovered that the lowest point of the tank is actually where the flexible tube going to the pump connects to the tank.  I am considering installing a "T" at this point, reconnecting the pump feed to one side of the "T" and running a new tank drain line from the other side of the "T" to a new tank drain valve so the tank drains completely.  Has anyone else noted this drain problem or tried the solution I am considering?

Thank you for your help.

BTW: I did notice a lot of algea was in my fresh water drinking hoses this year. I don't know if it was there before and I didn't notice. I was using them to spray the camper to find a leak, and noticed the camper kept getting stuff running down. I have bought all new drinking hoses, and will make sure I sanitize those each year too. 

If you find one be sure its a black watertank and not a blackwater tank.
 

Yeah, I haven't done it yet, but I always sanitize at the beginning of the season and again anytime I haven't used the system for a couple of months. 

I do like the idea of a tee at the low point of the plumbing, unless the actual low point drains would suffice.

I'd still want to sanitize the tank regularly even if I knew all water was out of the tank or it was painted black.

TT

That's what many of us do. I bring a couple of those 2.5 gallon disposable plastic water dispensers and set one up on the counter while camping. I put it in the sink while travelling in case it leaks. Two last us well over a week.

Just a thought..

As for algae in the tank, there are a lot of products on the market that the sellers claim remove the algae and get rid of bad taste and odors.  Here's one from West Marine: http:// www.westmarine.com/buy/west-marine--water-tank-flush-cleaner--14044424 -  https://www.westmarine.com/buy/west-marine--water-tank-flush-cleaner--14044424

Since we don't make a practice of drinking tank water we just flush the tank and pipes with a bleach solution every so often, which is plenty good for non-consumption purposes. 

Pool shock took care of it, cleared it in about 8 hours. Pool shock might work well in the rpod FWT actually....

Use of strong chemical agents, such as pool shock, that are not designed for the small scale fresh water tanks of an RV, are likely contrary to chemical product labeling instructions.  At the very least, contact the manufacturer's help line to ask whether their product is safe for a potable water system and and how much to use.  

Offgrid. Sorry to take so long to reply, but here is the situation.  Noticed flecks of green algae when emptying tank even after sanitizing and repeated flushings.  Decided I really needed to see what was going on inside the fresh water tank.  First drained the tank.  Cut hole though floor of R-pod over tank.  Cut a five inch hole in the top of the tank (carefully, more details later).  Now that I could really see into the tank, I found a mess.  Algae had grown on the top, bottom and all sides of the tank interior.  Water sprayed through the hole with a garden hose dislodged only bits of the algae from the surfaces.  Also found that emptying the tank through the usual drain hole left several gallons of water in the tank.  As you suggested, removed the connection to the fresh water system and added a T for a new drain.  Helped to drain but still left a gallon or more at the deepest part of the tank. 

Clearly indirect sunlight does not kill algae.  Also algae must not be toxic for it has not sickened or killed me yet.  I suspect the algae has grown incrementally over the four years of owning the R-Pod.  The fact that it is impossible to really drain the tank each year unless one parks on steep downhill slope is an inherent problem in the tank design. Amazingly, I had observed no algae coming through the faucets and the pump filter was clear.  Cannot explain that.

What to do.  I have ordered a small high-pressure washer with an elbow to try to clean the tank surfaces of algae.  Will also try to remove last gallon of water and remaining algae with a wet/dry vac. Did not yet try to paint the tank black because I still want to see what is happening inside. 

Have lots of pix, but having some trouble adding to this post.  Will provide pix and more details later, e.g. cutting and sealing the five inch hole and the results of high pressure washing.  Thanks for your patience.  Taospod

W

Its not that difficult to install one. 

You might also consider installing a good water filter or drinking bottled water so you don't need to be concerned about getting ill from whatever is in there.