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Post by xixp on Oct 10, 2020 15:20:40 GMT -5
Hi To All,
Im having the following problem with my boat sump pump (its an Atwood with a 750 gph pump).
A while ago i replaced the pump because the floating switch stopped working; since then i noticed that the pump works but it doesn't take the water out. (Sump gets filled and pump runs without taking water out).
This happens when the AC is working, the ac outlet shares the same overboard discharge with the sump pump so i guess that the Ac flow creates back pressure at the pump?
If i move the pump to let some air in , it starts moving the water out.
When the ac is off ive tried filling the sump with water from the head sink and it works fine. Ive replaced the pump again and the problem remains; when the AC is on the sump gets filled and pump runs without taking the water out.
The sump has a rubber check valve that seals well but when i remove it after the pump has emptied the sump i get a lot of water from the line so im not sure if remaining water creates too much back pressure when the ac combines its flow with that remaining water in the line?
I believe ive had this problem since the boat was new but ihad never used a lot the AC as to notice the issue.
Ideas???
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Post by hawker63 on Oct 10, 2020 16:37:24 GMT -5
That’s an interesting problem and you’re probably correct that if the AC and Sump share the same thru hull fitting, it maybe that there’s too much water flowing thru the single fitting and the AC has more pressure so the Sump is deadheaded. Our boat has separate thru hulls for the 3 ACs and the 2 Sumps. This seems to be the best solution, but not sure you’re excited about drilling another hole in the boat. The other option is to try throttling the flow through the AC, can do it by partially closing the valve in front of the strainer or adding a valve after the AC pump and seeing if you can find a balance where less water goes thru the AC ( but enough to still cool the boat) and allow Sump to keep up.
Do you have any pictures of how they plumbed the 2 hoses to one thru-hull fitting, that may help with ideas.
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Post by xixp on Oct 10, 2020 17:24:56 GMT -5
Yes..i thought about adding a separate discharge for the sump but that would be my last resort..! Another detail is that once the AC is off; the sump pump keeps running without removing water (the sump 100% full) . Until a wiggle the pump a little to let it get some air it doesnt move any water either despite having the ac off. Once it starts working (no AC) it keeps working without issues. Another test i ve just done was to manually wipe dry the sump, removed the pump and rubber check valve and turned the AC on. There was no water coming from the hose that goes to the overboard discharge outlet where the AC discharges the cooling water. So...im puzzled because i dont understand what is creating the back pressure to the pump. What i believe to recall is that the original pump had an small hole somewhere in its outlet; replacement pump doesn't have any. May be the pumps included in the sump from the factory has it to somehow prime it..  |
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Post by xixp on Oct 11, 2020 20:12:43 GMT -5
Update and Fix...
After researching on line ive found that what i had was an “air lock” problem. It seems that its pretty common in sump pumps (any type of pump with its impeller at the bottom due to the fact that they are not self priming)
The recommended fix is to have a hole between the pump outlet and check valve to allow the pump to get rid of the air pockets that create the airlock.
The original pump had it but i didnt know it served above purpose.
Today i made an small hole in the Pump outlet Pointing to its side to minimize splash in the sump box and it worked as supposed.
I hope this helps to anybody having a similar issue.
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Post by gofast24 on Oct 12, 2020 10:54:34 GMT -5
Sump pumps shouldn't ever have any back pressure, just multiple drain hoses going into the box and then float switch senses high water level and turns on pump. Also, sump pumps are in a box and when water entrs bos they dont need to be self priming. Possible your sump pump discharge check valve is stuck closed (or open). I have replace 2X sump pumps 3 times, finally put in Johnson sump pumps with the electronic float level switches, no problems for 3 years now. With the electronic float switches you have to make sure your not putting really greasy water from sinks or shower drains, if so, the sensors on the switches get :greased" up and then just need to clean off with some hydrogen peroxide and a old tooth brush, back to working again. Good luck nd lrt us knmow how you make out!
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Post by tc33obx on Oct 12, 2020 16:10:01 GMT -5
That is interesting. I don't think my 4460 had that priming hole and it worked fine. However, I know after installing my check vales in my home Sump Pump well in my basement, I had to drill those priming holes in both the electric pump and the batter backup outlets to get them to work effectively. So I get the science. Not sure why I didn't have one in my 4460 sump.
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Post by xixp on Oct 12, 2020 16:44:36 GMT -5
Well...the Attwood data sheet of my sump mentions a vent to avoid the problem but its plugged in mine.
May be Regal decided that its better to have a sealed sump box with the pump venting hole than the box with the vent hole. (Im not sure if this hole is supposed to include a check valve..?).
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