Water pump short cycling

[dziedzicmj]

I have a standard water pump (for fresh water) in my Catalina C270. This season I noticed that the pump is short cycling (1-2 s period). In the past the cycles were much longer (10 s?). The difference this season is that I bypassed the water heater (I don't have much use for it and it never really worked that well). I don't have any accumulator in the system.
The question is: is it normal or my pump is developing some problem?
If i wanted to ignore the problem (if there is any), I would explain the situation by saying that in the past the water heater acted as, kind of, accumulator and there was more water volume to build the pressure (maybe even there was some air bubble in the water heater which would help even more).
Am I overthinking it? Is it pretty much normal?
thanks for any inputs

 

[Maine Sail]

It should not cycle at all with the taps turned off. If it does you have a leak or a bad pump. When turned on the pulse/on time of the pump will depend upon flow rate the faucets demand from the system. At low flow longer times between pulses and with full flow the pump may never stop. An accumulator is a great investment.

 

[LakeOntario270]

I have my water heater connected and the pump will cycle about 1 second every now and then with all the faucets off.

 

[kloudie1]

Like Maine said, that is either a leak in the piping (one of the 9 bajillion fittings drooling) or a leak in the pump valves or diaphragms.

 

[Maine Sail]

I have my water heater connected and the pump will cycle about 1 second every now and then with all the faucets off.

You have a leak or a bad pump, one of the two. To isolate the pump remove the system outlet hose and stick a short piece of hose with a ball valve on the end of it onto the pump. Now start the pump and purge the air from the short piece of hose and close the valve. It the pump stops cycling on & off the problem is in your system.

I generally use radiator pinch off pliers for this test but most boat owners don't have them..

Image courtesy HFT:

 

[Stu Jackson]

All of the water pumps are pretty much the same. And each and every one of them has a manual, and each of those manuals have Troubleshooting Guides at the back of them. They explain how to diagnose the potential issues, step-by-step. Good luck.

 

[druid]

Unlike the other responses, I'm going to assume the short-cycling is when you have a tap ON. This was happening in my boat, complete with water shooting out in spurts. The HW heater solved the problem. Yes, the heater acts as an accumulator (surge tank) and without it your pump will short-cycle. If you have lots of hose connected (like if you're taking the water to the galley and the head) the hoses will act as a bit of a surge tank and the flow will not be too bad.

But yeah - one of the reasons I put in a HW heater was to act as a surge tank. It works great!

druid

 

[dziedzicmj]

Unlike the other responses, I'm going to assume the short-cycling is when you have a tap ON.

This is exactly what I meant. When the tap is off, no cycling (if it was cycling I would have guessed that I have water leak).
Generally, I was looking for a confirmation that the water heater acted as an accumulator. From what I hear, it did.

thanks

mdz

 

[Stu Jackson]

I was looking for a confirmation that the water heater acted as an accumulator. From what I hear, it did.

I would surely like someone to explain to me how a water heater, which is just a longer pipe inside the heater, could possibly do this.

 

[WayneH]

Stu,

I'm not a plumber and I don't play one on TV. But searching through water heater cutaway images, I noticed that the hot water draw-off is not in a pipe. The engine coolant goes through the pipe coils but the domestic water is in a tank. The hot water draw-off does not come from the top of the tank but just a bit lower. This means there is gas above the water level that gets compressed when the pressure pump starts up. The compressed gas acts like an accumulator in the pressure water system. The one image I found was on www.ybw.com so I copied the image location to put is here and it's from MaineSail's website.
http://www.pbase.com/mainecruising/image/122792089.jpg

 

[woodster]

my fresh water supply runs a good while before the pump kicks in and will usually shut off before i have turned off the water tap but i have a 1 gallon accumulator and i have a hot water tank like in your pic i can draw water from the tap some times and the pump never comes on....... that accumulator is really the cat's meow

 

[odaydokay]

I presume your pump has a strainer? If so, pull it out and see if it is full of crap, if so clean it.