Cold water accumulator/pump issue

[Waterloo Sunset]

Hi

Looking for some advice/help please:

Recently, SWMBO commented that the freshwater water pump seems to take longer than usual to kick in, especially in the shower.  The pump is a Shurflo 2095-423-343 which runs at @10L/min with max pressure of 30psi.  The cold water accumulator is currently reading 1 bar or ~15psi with the pump off & taps open.  This is the first time I have ever taken a reading on the accumulator so I do not know if this is the correct pressure but, intuitively, it seems low based on the pump's max pressure.

Any assistance greatly appreciated.

[Tony Brooks]

7 minutes ago, Waterloo Sunset said:

Hi

Looking for some advice/help please:

Recently, SWMBO commented that the freshwater water pump seems to take longer than usual to kick in, especially in the shower.  The pump is a Shurflo 2095-423-343 which runs at @10L/min with max pressure of 30psi.  The cold water accumulator is currently reading 1 bar or ~15psi with the pump off & taps open.  This is the first time I have ever taken a reading on the accumulator so I do not know if this is the correct pressure but, intuitively, it seems low based on the pump's max pressure.

Any assistance greatly appreciated.

 

 

 

As a rough guide, set the accumulator to about half the cut-out pressure, so that suggest a cut-out pressure of about 30PSI - near enough for it to work.

 

It won't be the accumulator pressure. Slow to kick in is usually a symptom of a problem with the pressure switch system so stiff diaphragm, blocked hole allowing pressure into the chamber or a chamber full of scale. The pumps are stripable  but many find them not worth doing with the price of spares.

[Tracy D'arth]

The accumulator pressure is low, it should be the same as the cut IN pressure of the pump, not the cut out pressure. But I don't think that is the problem from your statement that the pump takes longer to cut in. That would suggest to me that either the pump is partially furred up in the port to the pressure switch or the switch itself is failing.

[Waterloo Sunset]

Thank you for both replies.

 

Further "tests" show no delay on using the cold taps in galley or bathroom, slight delay (~5 seconds) on the hot taps, but considerably longer delay (~15 seconds sometimes!) when using the mixer shower.  Could this be due to the low flow rate through the shower head (one of those ionic bead high pressure gadgets) and the long run from accumulator to the calorifier back to the bathroom which is in the middle of the boat?

 

I will put another 5psi in the accumulator since it is low anyway, thanks TD'.

[Tracy D'arth]

2 minutes ago, Waterloo Sunset said:

Thank you for both replies.

 

Further "tests" show no delay on using the cold taps in galley or bathroom, slight delay (~5 seconds) on the hot taps, but considerably longer delay (~15 seconds sometimes!) when using the mixer shower.  Could this be due to the low flow rate through the shower head (one of those ionic bead high pressure gadgets) and the long run from accumulator to the calorifier back to the bathroom which is in the middle of the boat?

 

I will put another 5psi in the accumulator since it is low anyway, thanks TD'.

Good call, descale the shower head in vinegar overnight and check the hose for collapse inside.

[ditchcrawler]

The pump wont cut in until the pressure at the pump falls below the cut in pressure. if you have one of those water saving crystal packed shower heads you will only be taking a small flow from the system and the pressure will take longer to fall. If you want to check this out turn on a cold tap until the pump runs, turn the tap off. Once the pump stops turn the tap on again and measure how much water you get before the pump cuts in. Now repeat with the shower head.

[nicknorman]

I would say the existing 15psi is about right. Better slighly on the low side than slightly on the high side. But as said, this is unrelated to the slow kicking-in of the pump.

[Waterloo Sunset]

13 minutes ago, ditchcrawler said:

If you want to check this out turn on a cold tap until the pump runs, turn the tap off. Once the pump stops turn the tap on again and measure how much water you get before the pump cuts in. Now repeat with the shower head.

Science! I will do this tomorrow and report back.  My guess is they will deliver the same volume/mass but I will let you know.  Thank you

 

11 minutes ago, nicknorman said:

Better slighly on the low side than slightly on the high side

Thanks Nick, I will leave as is then.

[ditchcrawler]

3 hours ago, Waterloo Sunset said:

Science! I will do this tomorrow and report back.  My guess is they will deliver the same volume/mass but I will let you know.  Thank you

 

 

It should

[Cas446]

6 hours ago, Waterloo Sunset said:

Further "tests" show no delay on using the cold taps in galley or bathroom, slight delay (~5 seconds) on the hot taps,

You should also have an expansion bottle on the hot side, if the expansion bottle pressure has dropped below the pump cut out pressure it will be acting as a second accumulator on the hot side only (depends on where the NRV is located) has your calorifier PRV been dribbling recently?

Edited September 29, 2021 by Cas446

[Brian422]

Suggest checking Fresh Water Tank Pickup by blowing back towards tank to ensure pickup is clear.

As can be seen from attached before and after photos, pickup my well have calcified over time.

Obscure but might help.

[Tony Brooks]

11 minutes ago, Brian422 said:

Suggest checking Fresh Water Tank Pickup by blowing back towards tank to ensure pickup is clear.

As can be seen from attached before and after photos, pickup my well have calcified over time.

Obscure but might help.

 

 

That would typically cause the opposite effect, the pump turns on as usual but takes much longer to turn off.

[Tracy D'arth]

10 hours ago, Cas446 said:

You should also have an expansion bottle on the hot side, if the expansion bottle pressure has dropped below the pump cut out pressure it will be acting as a second accumulator on the hot side only (depends on where the NRV is located) has your calorifier PRV been dribbling recently?

Only if there is an NRV on the feed to the calorifier, most boats don't have.

[Waterloo Sunset]

13 hours ago, ditchcrawler said:

It should

They did.  Confirmed also that, if I run the tap slowly (simulating low shower flow), there is a delay on the pump kicking in.

 

11 hours ago, Cas446 said:

You should also have an expansion bottle on the hot side, if the expansion bottle pressure has dropped below the pump cut out pressure it will be acting as a second accumulator on the hot side only (depends on where the NRV is located) has your calorifier PRV been dribbling recently?

No expansion tank on the hot side and the PRV dribbles whenever calorifier is heated by either the Eber or the engine.

 

I guess the next question (assuming everything appears to be working as intended), is, is there a modification I can make to the system (other than the obvious "fit a high flow head") to overcome the impact of the low flow/high pressure shower-head?

 

Thanks to everyone for their help so far, much appreciated!

Edited September 30, 2021 by Waterloo Sunset

[Tony Brooks]

39 minutes ago, Waterloo Sunset said:

They did.  Confirmed also that, if I run the tap slowly (simulating low shower flow), there is a delay on the pump kicking in.

 

No expansion tank on the hot side and the PRV dribbles whenever calorifier is heated by either the Eber or the engine.

 

I guess the next question (assuming everything appears to be working as intended), is, is there a modification I can make to the system (other than the obvious "fit a high flow head") to overcome the impact of the low flow/high pressure shower-head?

 

Thanks to everyone for their help so far, much appreciated!

 

1. In an ideal world, fit an expansion tank to the hot system to stop the PRV dribbling and minimise the stress on the calorifier.

 

2. I am not clear what the problem is. You now know it is related to low flow rates and is to be expected, so why do you need to do anything. By all means blow the accumulator up to the pump cut OUT pressure, but I don't think it will make any difference. Once the pump is running, it will just be a case of a longer off period than with a tap. Unless you either have an outflow from an outlet that is greater than the pump's delivery volume  you will get the pump cycling - that is it, end of. From this, you can conclude a higher output shower head or having another tap running while showering are about the only way to minimise cycling.

[Waterloo Sunset]

1 hour ago, Tony Brooks said:

 

1. In an ideal world, fit an expansion tank to the hot system to stop the PRV dribbling and minimise the stress on the calorifier.

 

2. I am not clear what the problem is. You now know it is related to low flow rates and is to be expected, so why do you need to do anything. By all means blow the accumulator up to the pump cut OUT pressure, but I don't think it will make any difference. Once the pump is running, it will just be a case of a longer off period than with a tap. Unless you either have an outflow from an outlet that is greater than the pump's delivery volume  you will get the pump cycling - that is it, end of. From this, you can conclude a higher output shower head or having another tap running while showering are about the only way to minimise cycling.

Thanks Tony.

 

When we get to our Marina for winter, I will look at getting an expansion tank and NRV fitted on the hot side.

 

After reading your second point, I realise I haven't explained myself well enough and missed out some possible key info;

 

The shower will run, the flow will slow down/stop and the pump delay on kicking back in means SWMBO is left with no water flow.  The time from water flow slowing to the pump kicking in is what I am tying to rectify, 

 

Apologies, for any confusion, I should have made this clear earlier.

[Tony Brooks]

Just now, Waterloo Sunset said:

Thanks Tony.

 

When we get to our Marina for winter, I will look at getting an expansion tank and NRV fitted on the hot side.

 

After reading your second point, I realise I haven't explained myself well enough and missed out some possible key info;

 

The shower will run, the flow will slow down/stop and the pump delay on kicking back in means SWMBO is left with no water flow.  The time from water flow slowing to the pump kicking in is what I am tying to rectify, 

 

Apologies, for any confusion, I should have made this clear earlier.

 

Ah, take the hose off both ends and look for either a restrictor/small bore rubber washer or a small strainer that might be furred up. Ditto, look in the shower mixer valve inlets for strainers. As others have said, descale the shower head and make sure there are no service valves on the supply to the mixer that are partially closed.

 

If the pump  cycles properly when a tap is open then it's probably not anything to do with the pressure switch, but if it runs all the time with a tap open then I would suspect a pressure switch problem  as I described  earlier.

 

On a properly working system the minimum pump off pressure should be similar from any outlet, you seem to have a longer "off" period just on the shower, so either something is keeping the pressure up in the rest of the system (a blockage to the shower) or for some odd reason the pressure switch won't close properly when the shower is running, but the two are not really connected apart from by pressure. The only explanation I can come up with is that the taps pass so much water the pump never turns off, but the shower passes less, so it does. It may be that the pump output is low because of either a blocked inlet (valve partially off, rusted up feed pipe, blocked pump inlet strainer) so it can't keep up with the flow from taps but can with a low flow shower head. If it is low flow, then the valves on one or more pumping chambers may be jammed open by muck or old age.

[Waterloo Sunset]

I will check all you have suggested but this bit;

6 minutes ago, Tony Brooks said:

if it runs all the time with a tap open then I would suspect a pressure switch problem  as I described  earlier

makes me think the pump is goosed - I will certainly check the holes for scale or other blockages.

 

Thanks once again.