With the pump in the right place you could enter the tank at the bottom of the side and only have two 45 degree elbows in the intake line. Each fitting in a pipe acts as a flow resistance and causes a pressure drop so you want the minimum number of fittings. Considering that the pump will be putting a large amount of negative pressure on the intake, I think RV sewage hose might collapse with a large strong pump. Schedule 40 PVC has been adequate for the intake of my pump and is relatively inexpensive. As you say, if you only need a few feet then $8 a foot for flexible hose isn't so bad. This assumes that the hose is rigid enough to handle the partial vacuum. The maximum pressure differential between the inside and outside of the tube would be atmospheric pressure, and at your altitude that is less than 15psi even if your pump could pull a perfect vacuum.
Reducing the tubing to 2" either on the intake or the output will restrict the flow quite a bit. The cross sectional area of a 2" id tube is 3.14 sq.", while the area of a 3" id tube is 7 sq.", or 2.25 times as large. I can't answer if that would burn your pump. Even if it didn't, it would not be ideal.
Enlarging the tubing will reduce the flow velocity of the papercrete, which is not necessarily bad. My small pump will spray pc over 10' out of the end of the tube after it travels 100' and up 25', and I have to be prepared for that thrust. A 4" pipe has a cross sectional area of 12 sq.", an increase of 1.8 times a 3" tube. This should yield about 56% of the velocity while delivering the same volume of pc.
spaceman Duct tape is like the Force. It has a dark side and a light side, and it holds the universe together. All opinions expressed or implied are subject to change without notice upon receipt of new information.
On 9/9/2011 2:12 PM, ken winston caine wrote:
Spaceman wrote:
<snip> I would be tempted to mount the pump on the
tongue of the mixer and tie it directly into the bottom of
the tank.
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Thanks!
That shortens the hose and gets rid of nearly all the bends. And I feel so dense for not having thought of it. And that's why I'm so grateful for input from groups like this! Having multiple minds accessible is better than having only one.
Maybe heavy duty RV sewer hose, reinforced like crazy with a couple rolls of duct tape would be adequate for a super short (maybe 2') section of flexi intake pipe if I need a flex section (on either or both ends of rigid pvc pipe) to get from the tank outlet to the pump inlet? Or -- if I only need about 4 feet of the semi-rigid hose, then $8 foot is OK.
NEW QUESTION, SPACEMAN: Would I burn up the pump if I used 2" hose instead of 3" and adapted it at the connector ends. Or, conversely, would I run into problems if I used 4" hose instead of 3"? (I imagine it might not pump at all, but am new to trash pumps...)
-- ken
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