Plumbing Systems

[Chewbacka]

18 minutes ago, ditchcrawler said:

I can't see any good reason why the pressurising pump needs to be adjacent to the cold water tank, mine is under the Galley cupboards. It would seem a bit pointless to me to have a calorifier and not utilise the free hot water available from the engine for the sake of two pipes

Pumps are usually better at pushing than sucking, so it is common to put the pump near the source, that said, on a narrowboat I doubt it makes a big difference unless you use long 10mm or 15mm pipes to supply the pump, which is a bad idea.

[system 4-50]

My water pump is a Jabsco of the type that doesn't require an accumulator. It is 10 years old with admittedly low use.  It was expensive but I wouldn't have anything else.  It speeds up and slows down according to demand.  It doesn't cut in overnight.

My water pump is mounted 2 - 3 ft up the side wall of the boat and sucks water out of the tanks (2) about 10ft away from the top of the tanks using a dip tube.  I can leave the boat for 2 months and when I come back, the syphon between the tanks and the pump is still intact.  I can deliberately break the syphon when desired to give 100% confidence of no leakage when the boat is unattended short of a failure of tanks themselves (which are plastic).  There is no way I would have a pipe from the bottom of a tank, it is just an unecessary joint risk.

[Tony Brooks]

31 minutes ago, Chewbacka said:

Pumps are usually better at pushing than sucking, so it is common to put the pump near the source, that said, on a narrowboat I doubt it makes a big difference unless you use long 10mm or 15mm pipes to supply the pump, which is a bad idea.

I agree with that. When we bought out boat the pump, PRV and accumulator were under a bed in the back cabin. Not easy to access when others are on the boat. I moved them to under the dinette at the front but that was for access and spare space, not being near the water tank. In the old days with some domestic water pumps being centrifugal it made sense to site the pump low down and close to the tank to maximise the chances of it  self priming if you ran out of water so it would not surprise me the "locate near the tank" was a folk memory of that.

[Jen-in-Wellies]

11 minutes ago, Tony Brooks said:

I agree with that. When we bought out boat the pump, PRV and accumulator were under a bed in the back cabin. Not easy to access when others are on the boat. I moved them to under the dinette at the front but that was for access and spare space, not being near the water tank. In the old days with some domestic water pumps being centrifugal it made sense to site the pump low down and close to the tank to maximise the chances of it  self priming if you ran out of water so it would not surprise me the "locate near the tank" was a folk memory of that.

A common failure mode of water pumps ends up with them leaking from the body on the low pressure side. You don't notice because the pump isn't cutting in to maintain pressure. Jabsco reckon their pumps can prime at up to a 1m height, so on a lot of boats, the pump could be placed above the level of the top of the tank without problems. Doing this would prevent the tank contents leaking out by stealth when the pump fails. I have not done this! They also say to keep it within 2m horizontal of the tank. Mine is a lot further than that. More like 4m, but it is roughly level with the base of the tank. I suspect a combination of -1m head and >2m distance is a worst case that Jabsco are warning against.

Jen

[scb61]

34 minutes ago, system 4-50 said:

My water pump is a Jabsco of the type that doesn't require an accumulator. It is 10 years old with admittedly low use.  It was expensive but I wouldn't have anything else.  It speeds up and slows down according to demand.  It doesn't cut in overnight.

My water pump is mounted 2 - 3 ft up the side wall of the boat and sucks water out of the tanks (2) about 10ft away from the top of the tanks using a dip tube.  I can leave the boat for 2 months and when I come back, the syphon between the tanks and the pump is still intact.  I can deliberately break the syphon when desired to give 100% confidence of no leakage when the boat is unattended short of a failure of tanks themselves (which are plastic).  There is no way I would have a pipe from the bottom of a tank, it is just an unecessary joint risk.

I currently have an old built in water tank that is pretty grotty, it is a large tank forming the front end of the boat and it has an inspection hatch on the front deck which lets in rain water - it is awful and I plan to over plate the lot including the water inspection hatch/filler point, their is a bulkhead inside the boat for the water tank which I will cut out in so far as to allow a new stainless water tank to be slipped in.

The idea of having this tank with a syphon arrangement rather than a low point take off was not something I had thought of.

I would be interested to know of which of the Jabsco pumps you use? I am told I need I need about 11lpm flow and I am currently looking at a Jabsco Par Max 2.9 which is quite affordable for me. 

[blackrose]

1 hour ago, Tracy D'arth said:

Please call vessels vessels and open header tanks, tanks, then we don't get confused.

So we should be calling accumulator tanks accumulator vessels? I think virtually every contributor to this forum is guilty of that error. Even the manufacturers and chandlers are guilty.

 

Edited January 10, 2021 by blackrose

[PaulD]

2 hours ago, blackrose said:

So what is it (as an engineer) that you don't understand?

 

MIT graduates cannot power a light bulb with a battery. - YouTube

[Tracy D'arth]

To be pedantic. an open topped tank used as a water  store as in heating system header feed and expansion tank is a Cistern but I avoided that to prevent the loonies turning this thread into another lavatory thread.

[Jen-in-Wellies]

3 minutes ago, Tracy D'arth said:

To be pedantic. an open topped tank used as a water  store as in heating system header feed and expansion tank is a Cistern but I avoided that to prevent the loonies turning this thread into another lavatory thread.

Spoilsport. ?

[Tracy D'arth]

2 hours ago, scb61 said:

Well I am glad I asked the question:

 

On the cold water supply the accumulator stops the pump from hunting/switching unnecessarily and the calorifier is a part of the pressurised system with a pressurised expansion tank - if I am correct with that then I am good to go!

 

The CHS I am ok with.

You are right.  As long as you remember water expands when heated and needs somewhere to go you will not be far wrong.

[ditchcrawler]

4 hours ago, Chewbacka said:

Pumps are usually better at pushing than sucking, so it is common to put the pump near the source, that said, on a narrowboat I doubt it makes a big difference unless you use long 10mm or 15mm pipes to supply the pump, which is a bad idea.

All my pipework is 15mm

[Alan de Enfield]

31 minutes ago, ditchcrawler said:

All my pipework is 15mm

As is my (supply) push-fit pipework.

All 'waste' pipework is in 40mm (I think) grey solvent welded stuff.

[David Mack]

3 hours ago, PaulD said:

 

MIT graduates cannot power a light bulb with a battery. - YouTube

 

How very true! On my engineering degree course there were fellow students who wouldn't have known which end of a nail to place against the wood, and which to hit with the hammer.

[jpcdriver]

One other thought as to why it might be a good idea to have the water pump near the fresh water tank. If you get a leak 'downstream' from the pump you will get notification of it because the pump will keep kicking in. Any leak before the pump may go unnoticed for longer. I learnt this from experience when the screw on lid of my cold water filter between tank and pump worked loose. So I would suggest keeping the number of plumbing joins between tank and pump to a mininum.

[system 4-50]

4 hours ago, scb61 said:

I currently have an old built in water tank that is pretty grotty, it is a large tank forming the front end of the boat and it has an inspection hatch on the front deck which lets in rain water - it is awful and I plan to over plate the lot including the water inspection hatch/filler point, their is a bulkhead inside the boat for the water tank which I will cut out in so far as to allow a new stainless water tank to be slipped in.

The idea of having this tank with a syphon arrangement rather than a low point take off was not something I had thought of.

I would be interested to know of which of the Jabsco pumps you use? I am told I need I need about 11lpm flow and I am currently looking at a Jabsco Par Max 2.9 which is quite affordable for me. 

The exact model I have is no longer made.  I have emailed Jabsco & asked what is the current equivalent since it is not obvious from their website. 

 

 

Bloody merge strikes again:

In case it has not already been said, some accumulator/expansion tanks are non-potable so choose carefully.

Edited January 10, 2021 by system 4-50

[PaulD]

4 hours ago, scb61 said:

I currently have an old built in water tank that is pretty grotty, it is a large tank forming the front end of the boat and it has an inspection hatch on the front deck which lets in rain water - it is awful and I plan to over plate the lot including the water inspection hatch/filler point, their is a bulkhead inside the boat for the water tank which I will cut out in so far as to allow a new stainless water tank to be slipped in.

The idea of having this tank with a syphon arrangement rather than a low point take off was not something I had thought of.

I would be interested to know of which of the Jabsco pumps you use? I am told I need I need about 11lpm flow and I am currently looking at a Jabsco Par Max 2.9 which is quite affordable for me. 

 

I use a Jabsco Par Max 2.9. Jabsco say in their advertising that it doesn't need an accumulator but I had hammering when turning off taps and it kicked in sometimes.in the middle of the night when the calorifier cooled down.  I emailed Jabsco about the hammering and they said I should have an accumulator in circuit. So I installed one and it now all works perfectly and  also doesn't wake us up at night. 

[Tracy D'arth]

44 minutes ago, PaulD said:

 

I use a Jabsco Par Max 2.9. Jabsco say in their advertising that it doesn't need an accumulator but I had hammering when turning off taps and it kicked in sometimes.in the middle of the night when the calorifier cooled down.  I emailed Jabsco about the hammering and they said I should have an accumulator in circuit. So I installed one and it now all works perfectly and  also doesn't wake us up at night. 

I have heard of this problem with these pumps before so I am dubious that it is a good idea to try to do without an accumulator so I will carry on doing it the way I know always works.

Night time contraction on  cooling down is always going to occur, so the pump must cut back in eventually.

[Tony Brooks]

I think those pumps have a bypass valve in then so that as they approach cut out pressure the valve opens and diverts excess flow back into the inlet. That has two problems as far as I am concerned. First that valve's opening pressure is set so if you alter the cut out pressure it ether wont open or odd things will occur. Secondly that valve setting must be close to the cut-out pressure so water surges when a tap is turned off (sub water hammer levels) is likely to jump the valve open, drop the pressure so the pump comes on again and so it goes on. I am with Tracy - fit an accumulator and I would add a basic pump.

[blackrose]

3 hours ago, Tracy D'arth said:

I have heard of this problem with these pumps before so I am dubious that it is a good idea to try to do without an accumulator so I will carry on doing it the way I know always works.

Night time contraction on  cooling down is always going to occur, so the pump must cut back in eventually.

Night time contraction and pump activation can also occur with an accumulator in the system depending on where the water pressure is in the cycle, which is why I always switch my pump off at night. 

 

I hate getting woken up in the middle of the night by the pump going off. Mine is under the bed so it's a bit of a shock to the system.

Edited January 10, 2021 by blackrose

[NB Alnwick]

Just to add my twopenn'orth to the excellent advice already given: Think about easy access to change the pump and keep a spare one as insurance against the time when the pump fails - which it will and usually when you are miles from anywhere! For the same reason we always have a kettle full of water on top of our stove.

 

Also while thinking of plumbing, have a good think about heating - we have radiators in the wash room, main cabin and bed 'ole - all fed from a back boiler using thermal circulation - so no pump to fail. Having said that, as with many boats the coldest bit is round your feet and I have often wondered why the return pipe on our central heating wasn't run under the floor to provide underfloor heating in the main cabin. Unfortunately, with our oak floor it would be too big a job to make retrospective changes.

1 hour ago, blackrose said:

Night time contraction and pump activation can also occur with an accumulator in the system depending on where the water pressure is in the cycle, which is why I always switch my pump off at night. 

 

I hate getting woken up in the middle of the night by the pump going off. Mine is under the bed so it's a bit of a shock to the system.

Switching the pump off at night and when you leave the boat unattended is good practice. Pumps and pipes have a habit of failing and leaking at the most inconvenient of times.