Water Pressure Problem

[jviss]

After speed-reading the replies, I don't think anyone mentioned a clogged filter on the pump input. It sounds like the pump is starved for water, be it an empty tank or blockage of the line. Maybe even a kink in the line or something squeezing it? When I empty my water tank, I get those very conditions. FWIW, the last thing I do when locking the boat up is turn off the water pump breaker and openeing the faucet to relieve pressure on the hoses. Cheap insurance.

Ron, something like that might be contributing. I have to check. There's a strainer at the manifold that collects the two tank lines, and it's clean. Then the supply to the pump disappears into the woodwork and emerges at the pump, high up in the port cockpit locker.

I know my supply side piping is undersized; the spec form Jabsco is that for runs over 48" the internal diameter of tubing should be 5/8" minimum; mine is 3/8". This is a huge difference! The area of 5/8" tubing is almost 3 times that of 3/8". So there's that.

Second, my pump is mounted on a vertical surface. Jabsco says "The pump is equipped with vibration pads which are most effective when the pump is mounted upright on a solid surface." Their illustration shows it mounted on a horizontal surface. I don't have the mental energy to think about changing this, at this stage of the game.

I don't relieve the pressure. To do so "easily," I'd have to drain the two gallons of accumulator. To prevent that I could reach into the cockpit locker and close the ball valve at the bottom of the accumulator, and then turn the pump off and open a tap. But I have never done that in boats before. I used to enjoy how, after five days away I'd turn on the pump power and it wouldn't run - meaning I had pressure, no leaks. I honestly don't understand how holding pressure can damage or 'wear' a water system.

In any event, I'll try to figure out if the line to the pump input is clear. I'll evaluate the practicality of increasing the line size, 'though unless it's larger all the back to the tank I don't think it will help to increase it just from the manifold.

I ordered the pump service kit and a new pressure switch. Can't hurt, I figure.

 

[Ron20324]

... Jabsco says "The pump is equipped with vibration pads which are most effective when the pump is mounted upright on a solid surface." Their illustration shows it mounted on a horizontal surface. .

I bought a Jabsco to install an anchor washdown system under the vee berth. It was so much easier if I could mount the pump upside down, so emailed them. They said it can mounted in any direction, it's just that when upright, if it leaks, it will not run down into the electrics.

 

[jviss]

Thanks, good to know!

 

[jssailem]

it's just that when upright, if it leaks

IF? more likely when.... All pumps are going to leak eventually. I think it is in their DNA... (definite, navigable, aperture)

 

[jviss]

Update: problem solved.

I rebuilt the pump. The kit was $100 on eBay, and contained the two pulsation dampers (molded rubber), intake and exhaust valves, diaphragm (rectangular, flat, rubber piece with some holes), and a belt. It came apart easily. The inside of the pump and the old rubber parts smelled really bad, and the smell persisted on anything they touched! There was a pencilled note saying it was last rebuilt in 2006. There was nothing obviously wrong, 'though the diaphragm was crummy looking and had taken a set. The washers on either side of it were not properly lined up. One threaded hole for the upper body was stripped, but I think the remaining three are holding well enough. Rebuild was a breeze. I checked the pressure switch and visibly it looked good.

I installed a pressure gauge. ($7.45 on Amazon, 45 for the 1/8"x 1/2" brass adapter to connect to the Parker connector I had on hand.) (One thing I love about this LLDPE tubing and Parker® O Ring/Grab Ring Tube Fittings is that with only just an inexpensive tubing cutter it's very easy to cut, change, splice things together, no other tools required, and no leaks!)

So far, so good. The pump works perfectly now. The pressure is running between 10 to 12psi at the low, and 28 to 30psi at the high. It's spec'd for 20 to 40. The new pressure switch is at home ($25 on eBay), will install it next week, which is very easy to do. (It appears I could have played with a spacer in the existing switch to raise the pressure; maybe the spring is worn out. But it's not designed to be adjustable.)

2018-10-06 16.09.13

• jviss
• Oct 7, 2018

2018-10-06 16.09.20

• jviss
• Oct 7, 2018

 

[Scott T-Bird]

I wonder if the small diameter source lines affect the overall life of the pump. When I first installed my system, I used 1/2" PEX (3/8" i.d.) with 90 degree bends and starved the pump. Got very low pressure. I changed the line from the tank to the pump to 3/4" flexible hose (only reducing to 1/2" at the pump fitting) to avoid friction-inducing bends. Now the pressure is very good. I would increase the size of the run if I were you. I don't know if the pump has to work harder to generate the pressure when there are smaller diameter lines or not, but I suspect it could be an issue.

 

[jviss]

I would increase the size of the run if I were you.

Yes, it's tempting to fix this, but it's a huge job for something that is working O.K. As I stated previously,

I know my supply side piping is undersized; the spec from Jabsco is that for runs over 48" the internal diameter of tubing should be 5/8" minimum; mine is 3/8". This is a huge difference! The area of 5/8" tubing is almost 3 times that of 3/8". So there's that.

I think I'd have to run the larger tubing all the way back to the tanks. That would mean perhaps changing the fittings on the tanks, and making a new manifold with tank shut-offs and strainer, and fishing all this stuff through the boat. And, 5/8" internal tubing is a lot bigger, and could be tough to pull and route. The stuff I used isn't available in 5/8" ID, but is available in 0.600" ID, which is pretty close. It's 3/4" OD. The fittings I used are not available in this size. The largest ID I can get in the same fitting family is 1/2" While going from 3/8" ID to 5/8" ID would triple the projected area, going to 1/2" would double it (0.11 to 0.19 to 0.31" for 3/8, 1/2, and 5/8" ID, respectively). So, it's much better, but still under the minimum recommended ID for that pump.

Still, a big job for dubious gain.

 

[Gunni]

Take the pressure up to 40-50 psi. If that doesn’t make you happy start with larger supply lines downstream of the accumulator.

 

[dlochner]

Remember, increased water pressure yields increased water consumption, which may or may not be an issue for you.

 

[jviss]

Take the pressure up to 40-50 psi.

The stock, non-adjustable pressure switch is supposedly 20 to 40pis, i.e., no at 20, off at 40.
It's working fine now that the pump is rebuilt, at 10 to 30psi, but I'll go ahead and install the new switch and see what happens.

 

[Gunni]

The pressure switch Capta mentioned would replace your pump switch, mount at the accumulator, and be infinitely adjustable. It would control your pump on/off power. A great suggestion.