Water pump cycling

[blackrose]

My water pump keeps going off and I can't find any leaks - although I'll need to remove the wooden covers over the pipes to know this for sure. It's not due to the calorifier cooling and reducing pressure because I left the immersion on last night and it was still happening. I don't have a non-return valve upstream of the pump so perhaps the pump's own valve is failing and it's pumping water back through itself to the non-pressurised side. Is this more likely to happen when the pump gets old?

[smileypete]

My water pump keeps going off and I can't find any leaks - although I'll need to remove the wooden covers over the pipes to know this for sure. It's not due to the calorifier cooling and reducing pressure because I left the immersion on last night and it was still happening. I don't have a non-return valve upstream of the pump so perhaps the pump's own valve is failing and it's pumping water back through itself to the non-pressurised side. Is this more likely to happen when the pump gets old?

 

I'd put the pump inlet hose into a small bowl/jug of water and watch what happens over time as the pump cycles.

 

If the level drops there is a leak somewhere.

 

If the level stays about the same it could well be the pump chamber valves are failing or obstructed.

 

cheers,

Pete.

[blackrose]

I'd put the pump inlet hose into a small bowl/jug of water and watch what happens over time as the pump cycles.

 

If the level drops there is a leak somewhere.

 

If the level stays about the same it could well be the pump chamber valves are failing or obstructed.

 

cheers,

Pete.

 

Thanks. If I'm disconnecting the inlet side then I may as well install a NRV and see what happens.

 

Mike

[tomandsophie]

I had exactly the same problem, and I solved it (on the advice of a very kind person on these forums) by letting some water out of the calorifier by twisting the pressure release valve. I don't know why it worked but it did. Worth a try.

[chris w]

tomandsophie

 

I suspect what cured your problem is not the letting out of water through the PRV but the fact that the PRV was probably dribbling (not sealing properly due to calcium build-up or whatever). Your twisting it to let some water out, removed the small piece of crud and the PRV thereafter sealed properly.

 

Mike (Blackrose).... this may well be your issue too. Try twisting the PRV a few times.

 

Chris

[blackrose]

tomandsophie

 

I suspect what cured your problem is not the letting out of water through the PRV but the fact that the PRV was probably dribbling (not sealing properly due to calcium build-up or whatever). Your twisting it to let some water out, removed the small piece of crud and the PRV thereafter sealed properly.

 

Mike (Blackrose).... this may well be your issue too. Try twisting the PRV a few times.

 

Chris

 

Thanks but it wasn't the PRV - I'm off to buy a NRV.

[GUMPY]

Thanks but it wasn't the PRV - I'm off to buy a NRV.

 

Strikes me that allthough this may cure the symptoms it wont cure the problem.

Could be better to investigate furthur, Any water system if built corectly should function without a NRV.

As said earlier it could be that there is a leak in the pump, if this is the case then it will only get worse (even with the NRV, allthough you wont notice it) until the pump stops working.

 

Julian

[Silkhay]

Strikes me that allthough this may cure the symptoms it wont cure the problem.

Could be better to investigate furthur, Any water system if built corectly should function without a NRV.

As said earlier it could be that there is a leak in the pump, if this is the case then it will only get worse (even with the NRV, allthough you wont notice it) until the pump stops working.

 

Julian

 

I had a similar problem and discovered on striping down the pump a bui;ld up of crud (calc) on the rubber diaphram valve within the pump, don't know the proper name, wipped/washed this off, re-assembled, problem solved.

 

Good luck

 

Martin

[blackrose]

Strikes me that allthough this may cure the symptoms it wont cure the problem.

Could be better to investigate furthur, Any water system if built corectly should function without a NRV.

As said earlier it could be that there is a leak in the pump, if this is the case then it will only get worse (even with the NRV, allthough you wont notice it) until the pump stops working.

 

Julian

 

Well if there's no leak in the system it can only be pressure backing up through the pump. If I fit the NRV I can't see how the problem can get worse? Yes the pump will stop working eventually - that's a given. It's 3 years old so it's probably on its way out already. I'll squeeze as much life as I can get out of it.

[Tony Brooks]

Well if there's no leak in the system it can only be pressure backing up through the pump. If I fit the NRV I can't see how the problem can get worse? Yes the pump will stop working eventually - that's a given. It's 3 years old so it's probably on its way out already. I'll squeeze as much life as I can get out of it.

 

 

This is a perfectly sensible approach to the problem. Not only do the silly plastic "valves" get crud under them they also get hair balls trapped under them - WITH a pre-filter - so a NRV is a quick & simple modification that is easy to clean without stripping a plastic bodied pump.

[blackrose]

This is a perfectly sensible approach to the problem. Not only do the silly plastic "valves" get crud under them they also get hair balls trapped under them - WITH a pre-filter - so a NRV is a quick & simple modification that is easy to clean without stripping a plastic bodied pump.

 

Thanks. I've just had lunch and will now do the job. I'll clean the strainer at the same time but I'm going to avoid taking the pump apart if I can.

 

Incidentally, if you have an accumulator it can be difficult to know if your pump is cycling intermittently because the accumlator takes it up and you may not notice it. For this reason I have an isolator valve on the accumulator. It makes diagnosis a bit easier.

Edited March 19, 2008 by blackrose

[blackrose]

Sawtid! (Or at least postponed!)

 

Thanks

[blackrose]

It seems I spoke too soon.

 

Although the NRV has cured the problem it's made the water pump hellishly noisy and rattley!

 

Waterflow to the taps does not seem to have been restricted. Does anyone know what's going on?

 

The NRV is a Speedfit double check valve http://www.bhl.co.uk/product.php?productid=48221

[smileypete]

It seems I spoke too soon.

 

Although the NRV has cured the problem it's made the water pump hellishly noisy and rattley!

 

Waterflow to the taps does not seem to have been restricted. Does anyone know what's going on?

 

The NRV is a Speedfit double check valve http://www.bhl.co.uk/product.php?productid=48221

 

Where's the NRV, right next to the pump inlet? And is there a strainer on the inlet?

 

How is the pump connected to the plumbing, rigid plastic pipe/PVC hose/rubber lined flexi hoses?

 

cheers,

Pete.

[blackrose]

Where's the NRV, right next to the pump inlet? And is there a strainer on the inlet?

 

How is the pump connected to the plumbing, rigid plastic pipe/PVC hose/rubber lined flexi hoses?

 

cheers,

Pete.

 

I fitted the NRV about 5" before the pump and there is a strainer on the inlet.

 

The pump is connected to the plumbing with PVC hose.

 

The noise from the pump ws back to normal when I came back from the pub last night and when I investigated I found a small leak in the pump between the head and the body. This leak wasn't there before I fitted the NRV, so it seems that the pump was backing up and now I've installed the NRV that back pressure has nowhere to go so it's forcing a leak.

 

Is it time for a new pump?

Edited March 20, 2008 by blackrose

[RLWP]

I fitted the NRV about 5" before the pump and there is a strainer on the inlet.

 

The pump is connected to the plumbing with PVC hose.

 

The noise from the pump ws back to normal when I came back from the pub last night and when I investigated I found a small leak in the pump between the head and the body. This leak wasn't there before I fitted the NRV, so it seems that the pump was backing up and now I've installed the NRV that back pressure has nowhere to go so it's forcing a leak.

 

Is it time for a new pump?

 

Maybe. It sound like the valves in the pump are leaking, allowing water to pass back through the pump. Before you fitted the NRV the water would leak back to the tank, and the pump would cut in when the pressure had dropped. Now the water leaks back through the valves raising the pressure in the inlet pipe to the pump causing the leak you found. I think you already understand this.

 

I think you have three possible solutions : take the pump apart and try to clean the valves; buy and fit a replacement valve/diaphragm assembly; buy a new pump. If you have the time and inclination I would try solution 1, but if it were my pump I would buy a valve block.

 

Helpful?

 

Richard

[blackrose]

Maybe. It sound like the valves in the pump are leaking, allowing water to pass back through the pump. Before you fitted the NRV the water would leak back to the tank, and the pump would cut in when the pressure had dropped. Now the water leaks back through the valves raising the pressure in the inlet pipe to the pump causing the leak you found. I think you already understand this.

 

I think you have three possible solutions : take the pump apart and try to clean the valves; buy and fit a replacement valve/diaphragm assembly; buy a new pump. If you have the time and inclination I would try solution 1, but if it were my pump I would buy a valve block.

 

Helpful?

 

Richard

 

Thanks. I've ordered a new pump. When it arrives I'll fit it and then take the old one apart and perhaps keep it as a spare if I can fix it. The new pump is a Jabsco and they told me that any pump that's done nearly 3 years in a domestic application has done ok because all 12v pumps are designed for "occasional leaisure use"

Edited March 20, 2008 by blackrose

[smileypete]

I fitted the NRV about 5" before the pump and there is a strainer on the inlet.

 

The pump is connected to the plumbing with PVC hose.

 

The noise from the pump ws back to normal when I came back from the pub last night and when I investigated I found a small leak in the pump between the head and the body. This leak wasn't there before I fitted the NRV, so it seems that the pump was backing up and now I've installed the NRV that back pressure has nowhere to go so it's forcing a leak.

 

Is it time for a new pump?

 

One thing that could be worth doing is to take the pump apart, and put a thin bead of silicone leak sealer (like Fernox LS-X) around the edges of the diaphragm, and between the inlet and outlet sides.

 

Then do screws up gently, and wait for sealant to set before final tightening.

 

If this doesn't work it might be as well to get a new pump, then fix the old sometime and keep as a spare.

 

I wonder if too much leverage on the inlet/outlet connections can cause the pump to leak around the edge or internally.

 

cheers,

Pete.

[blackrose]

One thing that could be worth doing is to take the pump apart, and put a thin bead of silicone leak sealer (like Fernox LS-X) around the edges of the diaphragm, and between the inlet and outlet sides.

 

Then do screws up gently, and wait for sealant to set before final tightening.

 

If this doesn't work it might be as well to get a new pump, then fix the old sometime and keep as a spare.

 

I wonder if too much leverage on the inlet/outlet connections can cause the pump to leak around the edge or internally.

 

cheers,

Pete.

 

I think Shureflo pumps are notoriously prone to leaks. I've gone for a Jabsco this time because they're also supposed to be quieter. We'll see. I didn't go for the cheapest in the range because the flow rates of those are only really meant for 1 or 2 outlets. http://www.jabscoshop.com/item.asp?ls=Rule...AF0&id=2596

 

Incidentally, the guy from The Jabsco shop (Cleghorn Waring) where I bought the new pump said he'd never heard of anyone putting a NRV upstream of their pump and said it was unnecessary and may restrict flow to the pump. So perhaps we were all wrong about this apart from Julian (Idleness) of course.

[chris w]

Or the pump guy doesn't know what he is talking about. Afterall, if he were bright, would he be working in a pump shop????

 

The primary purpose of the NRV is to prevent warm water from the calorifier running back and mixing with the cold water at the pump and possbly allowing bacteria to grow at the warm interface. I'm not saying that bacteria WILL grow without an NRV fitted, as I'm no biologist, but that's the thinking behind it.

 

Chris

[blackrose]

Or the pump guy doesn't know what he is talking about. Afterall, if he were bright, would he be working in a pump shop????

 

The primary purpose of the NRV is to prevent warm water from the calorifier running back and mixing with the cold water at the pump and possbly allowing bacteria to grow at the warm interface. I'm not saying that bacteria WILL grow without an NRV fitted, as I'm no biologist, but that's the thinking behind it.

 

Chris

 

To be fair he was only talking about a NRV fitted upstream of the pump to cure back pressure through the pump, not the NRV next to the calorifier - I think most people accept that's a good idea as long as there's a suitably sized expansion tank in the system.

 

Not everyone is as ambitious as you Chris - that doesn't necessarily mean they aren't bright. The traits of intelligence and drive are sometimes mutually exclusive.

Edited March 21, 2008 by blackrose

[chris w]

To be fair he was only talking about a NRV fitted upstream of the pump to cure back pressure through the pump, not the NRV next to the calorifier - I think most people accept that's a good idea as long as there's a suitably sized expansion tank in the system.

 

Not everyone is as ambitious as you Chris - that doesn't necessarily mean they aren't bright. The traits of intelligence and drive are sometimes mutually exclusive.

 

Actually you don't need to have an expansion tank fitted to be able to fit an NRV as well - those two are mutually exclusive.

 

I agree drive and intelligence may not necessarily be linked but intellectual stimulation and intelligence usually are. I personally wouldn't find much intellectual stimulation selling pumps over the counter and don't believe you would either Mike. Ergo.........

 

Chris

[blackrose]

Actually you don't need to have an expansion tank fitted to be able to fit an NRV as well - those two are mutually exclusive.

 

I agree drive and intelligence may not necessarily be linked but intellectual stimulation and intelligence usually are. I personally wouldn't find much intellectual stimulation selling pumps over the counter and don't believe you would either Mike. Ergo.........

 

Chris

 

No, I'm not into the pump sales scene, but I used to have a friend who was a bit of an intellectual and spent most of his spare time reading heavyweight stuff. When we worked together in NZ on building sites and fruit picking, etc., he used to tell me how much he was looking forward to a nice sweeping job - just him & a broom and his thoughts elsewhere...

 

I thought if you had a NRV on the cold water inlet to your calorifier then an expansion vessel somewhere downstream of the NRV (or on the hot water outlet side from the calorifier) was recommended, otherwise you just have a pressure vessel? I'm not taking into account the PRV on the calorifier because as I'm experiencing at the moment, these things can fail - mine is dribbling, but if it got stuck without an expansion vessel the pressure may end up bursting the calorifier.

Edited March 21, 2008 by blackrose

[chris w]

No, I'm not into the pump sales scene, but I used to have a friend who was a bit of an intellectual and spent most of his spare time reading heavyweight stuff. When we worked together in NZ on building sites and fruit picking, etc., he used to tell me how much he was looking forward to a nice sweeping job - just him & a broom and his thoughts elsewhere...

 

I thought if you had a NRV on the cold water inlet to your calorifier then an expansion vessel somewhere downstream of the NRV (or on the hot water outlet side from the calorifier) was recommended, otherwise you just have a pressure vessel? I'm not taking into account the PRV on the calorifier because as I'm experiencing at the moment, these things can fail - mine is dribbling, but if it got stuck without an expansion vessel the pressure may end up bursting the calorifier.

 

The same would apply regardless of whether an NRV were fitted. In the event of a PRV not opening through failure, either the calorifier is going to blow or a pipe/joint downstream or upstream of the calorifier.

 

Chris

[blackrose]

The same would apply regardless of whether an NRV were fitted. In the event of a PRV not opening through failure, either the calorifier is going to blow or a pipe/joint downstream or upstream of the calorifier.

 

Chris

 

Except that without a NRV, assuming the cold water pipe is plastic it can take up some of that pressure build up - depending of course on how far the calorifier is from the pump. I think the NRV is installed not only to prevent the growth of bacteria in the cold water pipe, but also so that you're not losing heat from the calorifier down that pipe, which might also mean unwanted warm water coming out of your cold taps.

Edited March 21, 2008 by blackrose