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Post by Mr Stabby on Sept 9, 2018 16:22:53 GMT
Rooting around in the dark recesses beneath the galley sink today, I notice that this tank has been leaking. It hasn't been leaking a lot, but it has obviously been weeping for some time as it has deformed the shelving beneath it.  I'm not really familiar with narrowboat plumbing systems so I'll ask a question or two before I attend to this next weekend. I understand that its function is to store water under pressure, meaning that the pump does not need to run when a small amount of water is drawn. I can draw hot water without the pump running, however for cold water the pump always runs when the tap is opened. From diagrams on the internet it would seem that it should be plumbed in so that both hot and cold taps can be opened without the pump needing to run. Is that what normally happens on other folks' boats? Secondly, given that I probably draw far more cold water than hot, is it even worth having, or would I be better off removing it altogether and sealing off the pipe with an end cap? |
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Post by JohnV on Sept 9, 2018 16:35:01 GMT
these tanks can be used either as expansion or accumulator tanks ........ as an accumulator it is installed in the outlet line of the pump. It is basically to stop the pump "cycling" too quickly. Without an accumulator, at certain tap opening amounts the pump can "chatter" switching on and off rapidly. This has two disadvantages for the user. 1) the water flow can splatter out rather than flow smoothly and 2) it doesn't do the pump or it's pressure switch any favours.
As an expansion tank it is installed in the output of the hot water tank and is to accommodate the expansion as the water is heated.
just to add ..... it prevents the hot water system being over pressurised
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Post by Deleted on Sept 9, 2018 16:39:49 GMT
Are you sure it's not the expansion tank for the hot water system rather than an accumulator for the entire domestic water system?
If it's the former it will be tee into to the hot water system only.
The later it will be tee into the outlet from the water pump before the tee for the hot leg.
They have two different and entirely separate functions.
You can get away without an accumulator (pressure set at the pump cut in pressure)
You shouldn't do without a hot water expansion vessel - without it you may get the calorifier prv leaking as there is nowhere in the system to absorb the expansion of the water as it heats up - this is particularly true if there is a Non Return Valve in the calorifier cold inlet.
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Post by JohnV on Sept 9, 2018 16:41:57 GMT
You can get away without an accumulator (pressure set at the pump cut in pressure) You shouldn't do without a hot water expansion vessel - without it you may get the calorifier prv leaking as there is nowhere in the system to absorb the expansion of the water as it heats up - this is particularly true if there is a Non Return Valve in the calorifier cold inlet. Knew I should have waited until an adult answered with a pithy technical reply  |
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Post by Mr Stabby on Sept 9, 2018 16:47:30 GMT
Are you sure it's not the expansion tank for the hot water system rather than an accumulator for the entire domestic water system? If it's the former it will be tee into to the hot water system only. The later it will be tee into the outlet from the water pump before the tee for the hot leg. They have two different and entirely separate functions. On the survey it was described as an accumulator, personally I would describe it as a hot water expansion tank (hence the thread title). I'll get a new one from Swindlers next weekend. |
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Post by Deleted on Sept 9, 2018 16:51:17 GMT
I've got three of the bastard things!  These two are for the domestic water, an accumulator (blue one) should be for potable water - particularly if you drink the water from your tank. The red is the hot water expansion and is set to the same pressure as the PRV as per household pressurised water systems. This one is for the now pressurised webasto (identical to a combi boiler setup) squeezing this lot in to the engine bay of a cruiser not without its challenges!  The diaphragms do perish and split so the pressure the vessel is set to does need checking now and again |
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Post by Deleted on Sept 9, 2018 16:54:23 GMT
Are you sure it's not the expansion tank for the hot water system rather than an accumulator for the entire domestic water system? If it's the former it will be tee into to the hot water system only. The later it will be tee into the outlet from the water pump before the tee for the hot leg. They have two different and entirely separate functions. On the survey it was described as an accumulator, personally I would describe it as a hot water expansion tank (hence the thread title). I'll get a new one from Swindlers next weekend. It may have been described as an accumulator because the surveyor didn't know his arse from his elbow! Follow the pipe back and see where it's connected to, my gut is hot only as the best place to fit an accumulator is adjacent to the pump outlet (remember it needs to be before the hot leg tee) Expansion vessel are cheap as chips from Toolstation or Screwfix Looks about 8L 🍻🔨🚢👍 |
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Post by naughtyfox on Sept 9, 2018 16:58:17 GMT
We have one in our boat, an accumulator - I understand there is air in it at pressure of 2.7psi, so you get a smooth flow from the water pump instead of the water jumping out spurt! spurt! spurt!
Ours has a Schrader valve, and I pump it sometimes with a bicycle pump, and we have a decent pressure guage (Made in Germany) to check it.
What will happen when the day comes the rubber bag (?) inside splits - how will we know?
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Post by Deleted on Sept 9, 2018 17:08:00 GMT
We have one in our boat, an accumulator - I understand there is air in it at pressure of 2.7psi, so you get a smooth flow from the water pump instead of the water jumping out spurt! spurt! spurt! Ours has a Schrader valve, and I pump it sometimes with a bicycle pump, and we have a decent pressure guage (Made in Germany) to check it. What will happen when the day comes the rubber bag (?) inside splits - how will we know? 2.7psi? That sounds awfully low. I've a feeling that should be Bar and is the system pressure the EV may be set to. An accumulator should be set to the pump cut in pressure ie:- when the pressure falls far enough in the system for the pump to activate - the only way to accurately tell what that is is to connect a pressure gauge to the system, I have a washing machine appliance tee installed for draining the system, filing the boiler and testing system pressure. What pump do you have (I'm betting a Jabsco parmax 7....) www.jabscoshop.com/marine/pumps/pressurised-fresh-water-pumps/52600-0292-par-max-7-pressure-controlled-pump.htmRe the split:- You will pump like bollocks and nothing will happen If it is an EV the PRV may let by. If it is an accumulator the pump will cycle more often. All pressure checks whether an EV or accumulator should be done with the system cold and depressurised. |
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Post by Deleted on Sept 9, 2018 17:18:01 GMT
Rooting around in the dark recesses beneath the galley sink today, I notice that this tank has been leaking. It hasn't been leaking a lot, but it has obviously been weeping for some time as it has deformed the shelving beneath it. I'm not really familiar with narrowboat plumbing systems so I'll ask a question or two before I attend to this next weekend. I understand that its function is to store water under pressure, meaning that the pump does not need to run when a small amount of water is drawn. I can draw hot water without the pump running, however for cold water the pump always runs when the tap is opened. From diagrams on the internet it would seem that it should be plumbed in so that both hot and cold taps can be opened without the pump needing to run. Is that what normally happens on other folks' boats? Secondly, given that I probably draw far more cold water than hot, is it even worth having, or would I be better off removing it altogether and sealing off the pipe with an end cap? When, or if you get a new one, insulate it. They suffer horrendously from condensation. I made a jacket for it from an old sweatshirt. (Your old yellow tee won't suffice I'm afraid 😂). |
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Post by Mr Stabby on Sept 9, 2018 17:24:34 GMT
I'll have a closer look at it again tomorrow then, I had assumed it was leaking but the damage to the shelving may have been caused by dripping condensation.
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Post by naughtyfox on Sept 9, 2018 17:54:51 GMT
We have one in our boat, an accumulator - I understand there is air in it at pressure of 2.7psi, so you get a smooth flow from the water pump instead of the water jumping out spurt! spurt! spurt! Ours has a Schrader valve, and I pump it sometimes with a bicycle pump, and we have a decent pressure guage (Made in Germany) to check it. What will happen when the day comes the rubber bag (?) inside splits - how will we know? 2.7psi? That sounds awfully low. I've a feeling that should be Bar. What pump do you have (I'm betting a Jabsco parmax 7....) Well, I may be partially stupid, but I found the paperwork quickly. Yes, it says here 'expansion tank for water pump 2.75 bar' (but why have I written expansion tank? surely it's an accumulator?) (it's just to the outlet of the water pump) (and afterwards I have written 20psi = upper limit for accumulator).
Water pump is a Flojet "Quiet Quad" Model R4305-500 Serial No. 00459642 Milton Keynes (is that a good pump?) |
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Post by Deleted on Sept 9, 2018 18:02:45 GMT
2.7psi? That sounds awfully low. I've a feeling that should be Bar. What pump do you have (I'm betting a Jabsco parmax 7....) Well, I may be partially stupid, but I found the paperwork quickly. Yes, it says here 'expansion tank for water pump 2.75 bar' (but why have I written expansion tank? surely it's an accumulator?) (it's just to the outlet of the water pump) (and afterwards I have written 20psi = upper limit for accumulator).
Water pump is a Flojet "Quiet Quad" Model R4305-500 Serial No. 00459642 Milton Keynes (is that a good pump?)That's more useful! R4305-500A 12V PRESSURE CONTROLLED PUMP Flojet Pressure Controlled Diaphragm Pump 12v DC 25psi Cut-in, 35psi Cut out,13LPM Flow Connections for 13mm(1/2") bore hose Self Priming to 1.5M, Can Run Dry It is intended an accumulator in that location. You should set it to 25psi as per their specifications. I'd check it with a gauge myself but there is no real reason to doubt their figures Looks Ok, probably a better chance it will last longer than the Shurflo that I use, but at twice the price it ought to! |
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Post by naughtyfox on Sept 9, 2018 18:08:12 GMT
Only quality products in our boat  |
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Post by Deleted on Sept 9, 2018 18:15:19 GMT
Only quality products in our boat I have to say from the pictures you have posted your little tub has some half handy kit on it, whoever had it previously certainly didn't go for rock bottom price. You look to have chosen well 👍🍻 |
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