Holding Tank Slow Pumping

[Max Simmons]

So now that I have the vacuuflush working as it should, I pumped the holding tank as I had been doing a lot of flushing as I troubleshot and repaired the head.
After I got it set up, I could pump briefly, like 30-40 seconds before it would slow down and barely suck anything. I'd remove the pump nozzle from the deck plate and I could could hear air rush in, so figured that the air vent was blocked and again made a mental note to add replacing it to my to do list. To check this theory, I removed the vent hose at the tank to allow plenty of air to enter. I could see through the fitting and know that it was not blocked. Went back to pumping figuring this would solve the vacuum issue but no change. I'd remove the pump nozzle every so often to allow air back in. I'm wondering of there's sludge build up that is heavy enough to cause this? Any thoughts?
Thanks

 

[Comodave]

Sounds like sludge build up in the bottom of the tank. If the vent hose is removed and the fitting is clear to the tank then not much else could cause that. Can you see into the tank or get an inspection camera in to see what the tank looks like inside?

 

[O C Diver]

If you think it's sludge, this works well for breaking it down. Probably best to fill it to 25% of the tanks capacity, wait a few days, pump out and repeat.

https://www.trawlerforum.com/forums/s31/holding-tank-cleaning-easy-way-46357.html

Ted

 

[Comodave]

Ted, you beat me to that link. I used that procedure on my tank and it certainly helped. Going to do it again this year.

 

[Max Simmons]

Thanks Ted. Just ordered a bag of Sodium Percarbonate. Looking forward to giving his a try.

 

[Comodave]

Is your deck fitting a straight shot down into the holding tank? If it is you could use some sort of a dipstick to see if there is stuff on the bottom of the tank. Maybe stir it a bit if possible and it may break loose enough to get it pumped out. Maybe a garden hose and a PVC pipe to back flush the tank to open the pump out diptube.

 

[Bacchus]

baffling??
If air enters thru deck fitting relieving vacuum the discharge hose to tank connection must be clear enough to let the air into the tank.
Have you tried flushing with vent hose removed to see if there is air escaping?
Maybe connect water hose to tank vent fitting to back flush?

 

[Comodave]

Make sure you don’t have a vent filter before back flushing the vent.

 

[Max Simmons]

So I started this method of fill and pump. Went down to the boat last night to pump out and start the second cycle. I found the bottle of Tide detergent had blown out and leaked all over my work bench. I think what happened is that I used the tide cap to measure the Sodium Percarbonate and didn't rinse it off. Enough got in the bottle and caused it to swell and rupture, at least that appears to be what happened. At least work bench is now very clean.

If you think it's sludge, this works well for breaking it down. Probably best to fill it to 25% of the tanks capacity, wait a few days, pump out and repeat.

https://www.trawlerforum.com/forums/s31/holding-tank-cleaning-easy-way-46357.html

Ted

 

[Comodave]

Always good to have a clean work bench…

 

[ABfish]

Just a thought- I pumped my holding tank on Saturday. The dock hand suggested I flush both of the heads for a couple of seconds while he was pumping. Seemed to speed up the process, I assume by providing better venting for the tank.

 

[O C Diver]

So I started this method of fill and pump. Went down to the boat last night to pump out and start the second cycle. I found the bottle of Tide detergent had blown out and leaked all over my work bench. I think what happened is that I used the tide cap to measure the Sodium Percarbonate and didn't rinse it off. Enough got in the bottle and caused it to swell and rupture, at least that appears to be what happened. At least work bench is now very clean.

Visualize my first attempt. Take the cap off the holding tank and watch brown foamy stuff come out onto the deck. In hind sight, atleast the holding tank didn't explode.

Ted

 

[Comodave]

Just a thought- I pumped my holding tank on Saturday. The dock hand suggested I flush both of the heads for a couple of seconds while he was pumping. Seemed to speed up the process, I assume by providing better venting for the tank.

If your vent isn’t working well you need to fix that. You could crush the holding tank and you don’t want to do that. I added 2 1.5” vents to mine, one to each side of the boat.

 

[Kaniksu]

I just had this happen and checked all my hose clamps. They were all tight but I loosened the top clamp (there are two there) on the hose to deck fitting, raised it about 1/4 of an inch and tightened it. Problem solved! No more air.

 

[The Brockerts]

I've added a T fitting to my vent line right were the vent line leaves the tank. This way I can open the T fitting when I go to pump out and I'm sure the vent is wide open. I check my vent's monthly but like the idea of a very short vent line during pumpout as the vacuum at our pier is very strong, sometimes emptying 30 gallons in 45 seconds. Yes, I get a little odor in the boat sometimes, but it goes away in a few minutes. And yes, I have imploded a holding tank, not fun.

The Brockerts

 

[Bmarler]

I just had this happen and checked all my hose clamps. They were all tight but I loosened the top clamp (there are two there) on the hose to deck fitting, raised it about 1/4 of an inch and tightened it. Problem solved! No more air.

What was the symptom? Slow pumpout or flow stop and start?
I’m having some issues like that but I need to address the crappy vent line installation as a first step. But I’ll remember this if that doesn’t give me any joy.