Need expansion tank help please

[chubby]

Hello ,

 

Today i bought from Screwfix a 5 litre expansion tank to fit as hopefully the remedy of my constantly dripping PRV on my calorifier . To my understanding ( which is weak ) the excess pressure which builds inside the calorifier as the water heats will expand into the tank rather than trip the PRV . ? Am i correct to think this is a feasable solution ?

 

When i got the expansion tank onto the boat however it has a massive thread at the bottom which is not going to fit onto my plastic 15mm pipes . I thought it would be a case of just teeing it into the hot water after the calorifier .

 

i really really struggle with plumbing and i'd be prepared to fork out for a plumber but cannot get anyone out to my boat so i 'll struggle on so i apologise if this is all very basic - to me it isnt - its a nightmare .

 

So first things first : How on earth do i get an expansion tank to fit my 15mm plastic pipes cos the expansion tank from screwfix has a thread at the bottom that must be 20 mm or more ??

 

Shall i take it back and get one from Uxbridge boat centre or will they all look like this ?

 

To install it what is the procedure without soaking my bedroom

 

Once ive fitted the tank to the pipes i will then set about trying to understand the various adjustments relating to the pressures relating to the pump / Prv / expansion tank but first i need to get it actually fitted .

 

Any help will be greatly appreciated as its doing my head and apologies again if this is basic stuff but im a total dunce at plumbing ,

 

cheers

[blackrose]

It should solve your problem providing that there is a non-return valve on the cold pipe going to the calorifier. The NRV is there to stop hot water backing up the pipe and getting cold which wastes energy (if used with the immersion on shore power) and may also carry a risk of legionnaires. So systems without an NRV don't need a hot water expansion tank because the expansion is accomodated for in the cold pipe. Have a look at the cold water feed pipe to your calorifier and you will probably see a NRV within a metre or so from the calorifier.

 

Firstly check that your expansion tank from Screwfix has stainless or epoxy coated insides because I bought one from them and after about 3 years it rusted through and sprang a leak. You should T the tank into the hot water pipe with the appropriate fittings. Just take the tank to a plumbers merchants and tell them what you want to do or if you end up getting your tank from UBC tell them it has to T onto 15mm pipe. They should have the fittings including a push-fit fitting for the 15mm pipe going to the tank (the vertical piece of the T). You'll probably need some PTFE tape too. I like the gas PTFE in the yellow plastic reels. Wind a turn or two of tape against the male thread so it doesn't come off when you put the joint together.

 

Turn your water pump and main water tank isolator off before you cut the pipe. Assuming it's plastic pipe you can just use a Speedfit 15mm equal T but have the expansion tank all ready to go with it's own short length of 15mm pipe fitted. Try to imagine where the expansion tank is going to sit before any of this. I used a short flexible steel braided tap connector to allow the tank to go where I wanted it. Also don't forget to put the little ferrules into the pipes for any push-fit joints you make! This is imperative but easily forgotten.

 

Open a couple of taps before you cut the pipe (with a plastic pipe cutter) but expect some water so have some old towels ready. Edit: I've assumed your calorifier is vertical so water losses should be minimal - if it's a horizontal tank others may be able to advise on how best not to lose half a tank of water into your bilges, but it will probably involve draining the calorifier.

 

Before you open your main tank isolator and turn the pump back on, set your accumulator tank (assuming you have one) to 3 or 4 psi below the pump's cut-in pressure, and set your hot water expansion tank to 3 or 4 psi above the pump's cut-in pressure.

 

Hope it works!

 

Mike (currently sleepless in Sarajevo)

Edited October 22, 2013 by blackrose

[kevinl]

Screwfix's website doesn't list a 5 litre expansion tank, can you put up a link so we can see what you've bought. If we can figure out what the "massive thread" is then they'll be some solution.

K

[chubby]

blimey !!!

 

im shocked to get replies at this time . Thankyou .

 

i cant sort a link im afraid as the only thing im crappier at than plumbing is computers . The product number on the website & catalogue is 71018 if this helps . Sorry .

 

Just now been measuring the thread and it seems to be 22m . im thinking a tap connector would be suitable as it s thread is 22mm but the opposite end is 15 mm .

 

I dont entirely understand the Non return valve thing . Ive never seen one anywhere between the pump and the calorifier . I shall have determined look under the units in the galley first thing tomorrow but i dont think there is one .

 

I dont understand how / why i wouldn t need an expansion tank if there isnt a NRV ? My dripping PRV on the calorifier is a real problem and its ruined the woodwork of the cupboards which wil all have to be replaced but i thought the expansion tank was the solution but as i say i doubt i have a non return valve ?????????

 

cheers again - im v grateful

[blackrose]

Have you tried turning your PRV a few times to open the valve and dislodge any limescale that's possibly built up in it causing it to leak? It's spring loaded so just try turning it and it will shut itself off once opened.

 

The NRV just looks like a joint in the cold pipe.

 

It sounds like your PRV isn't plumbed out the boat through a skin fitting if it's caused damage to interior wood? I don't know why some builders/fitters do it that way?

Edited October 22, 2013 by blackrose

[Iain_S]

http://www.screwfix.com/p/expansion-vessel-8ltr/71018?_requestid=2559

 

The thread is likely to be a BSP one, probably 3/4" BSP, rather than metric. I note that it is sold as "suitable for heating and cooling systems", so likely to be similar to Blackrose's one.

 

Iain

[Rod a mod from Tod]

Selection of NRV here so you know what you might be looking for http://www.screwfix.com/search.do?fh_search=non+return+valve

 

There is also a more suitable exp vessel imo.

 

First I would do as previously suggested and give the blow off a bit of a tweak and see if it then reseats or perhaps you could even replace the blow off.

[dor]

I suspect the vessel has a 3/4 BSP male thread on it. You can easily pick up a 3/4 female bsp to 15mm compression connector then T it into your hot water side.

Check the pressure is not too high - if it is higher than the pump pressure it won't work. About 15psi suits most pumps. measure pressure with pump off and tap open.

Edited October 22, 2013 by dor

[nicknorman]

Firstly, I would prioritise plumbing the PRV so that it doesn't release water somewhere that can cause damage. Ours exits into the stern gland bilge area, alternatively it should exit through the hull. Even with an expansion vessel, a pump fault or PRV fault can result in water escaping via the PRV.

 

Secondly there is some confusion on here about the correct pre-pressure setting of the expansion vessel. It should be set to the cut out pressure of the pump (not cut in). That way, the vessel will remain empty when the pump cuts out, but start to fill as the pressure further increases due to thermal expansion. If the pressure is set lower than this, it will still work but since the vessel will be permanently partially full, its effective capacity is reduced - you might as well have bought a smaller vessel and pressurised it properly!

Edited October 22, 2013 by nicknorman

[Captain Fizz]

Where are you Chubby?

There are many reasons why prv's play up.

The pump pressure may be too high, the prv's spring may be tired. Prv's seating corroded or scaled and so the list goes on.

As advised up thread, they should always be installed to discharge either out of the hull or into a pumped bilge.

As also stated up thread, any expansion vessel needs to be stainless as the ones sold for heating systems are designed to run on a sealed system containing a corrosion inhibitor.

Happy to give you a hand if you are not a million miles away.

Cheers,

Simon.

[Dominic M]

Hi Chubby (it's quite amusing to be able to call someone "chubby" without receiving a smack in return!).

 

As Blackrose says above, the best thing to do is to plumb the outlet from the PRV overboard via a skin fitting. Plenty of boatyards should be able to do this for you. I'm sure High Line at Iver will if the yard at Uxbridge won't. It is not an expensive job, or shouldn't be. Your PRV may be faulty, but at times it should release excess pressurised water in the system as this is what it is designed to do. If it is dripping all the time then it is worth replacing, if twisting the red top a few times doesn't cure the problem. They don't cost much. Having an expansion tank means you'll have to empty it from time to time, because it can't return back through the pressure valve into a pressurised water system. If you come to sell the boat then a decent surveyor will pick up on that issue and the buyer will reasonably expect it to be put right anyway.

 

Dominic

[chubby]

Hello ,

 

Thanks again . The calorifier is a new one i put in in April . The old one seemed to have caused no problems at all for years but had no immersion coil . It had no PRV either and there seems to be no NRV between the pump and the calorifier . The previous owner kept the boat in a marina for a great deal of time and this marina has a shower block which is why they didnt need an immersion fitted.

I have a 240 v hook up so bought a 55 litre surecal upright calorifier under the impression that it would be a straight swap , wire up immersion and job done .

 

ive twisted the red knob on the PRV clockwise a few times . Theres a rush of steam and water . This passes into some pipe and into a 5 litre bottle i empty every 4 /5 days . There is NO audible click etc after i do this - should there be ? Yhis was meant to be my temporary fix and i hoped it would prevent further damage to the woodwork but i think the damage was already done .

 

Never mind . What i must do now before this drives me bonkers is get it sorted before i rebuild the cupboard but in a way that enables anyone taller than 4 ft to actually access the thing .

 

After the accumulator theres is a pressure reducing valve limiting the pressure to 2 bar . I fitted this as Surecal suggested the pressure from the pump might be tripping the PRV. . This hasnt sorted the problem. It appears therefore it must be pressure from expanding water / heat causing the PRV to trip .

 

I have switched off my immersion overnight and now the PRV doesnt drip so theres definately too much pressure inside caused by expansion if the water . The temperature is set to just below 60 as i believe its potentially unsafe to go below 55 due to legionaires disease (?) .

 

would this suggest i need an expansion tank regardless of non return valves being present or not ?

 

cheers

[trackman]

A Surecal calorifier will have an NRV built in, so it won't be easily visible. It will also limit options for draining the thing. I know cos when ours failed it was nearly impossible to empty, even with the leak it had! It does have the benefit of limiting water outflow when breaking into the hot water circuit though.

The EV will need setting to the right pressure after fitting. As Nikkorman says, it needs to be at or a little above your pump cut out pressure, and well below the pressure at which the EV opens. There will be a car tyre type valve on it, probably under a round plastic cover. Use a car tyre pressure gauge to check the pressure. Ours was supplied with far too high a pressure. If so, just release air as you would with a tyre, until it's right. If it needs more pressure a car tyre or cycle track pump will sort it. Excess pressure will mean the EV can't do its job & the PRV will keep dribbling. If the pressure is too low the pump will fill the EV partially as already said.

[chubby]

Hello again

 

 

Having now entirely removed all the surrounding cupboard and shelves i can now access the calorifier from all sides . Aswell as the dripping PRV theres the tiniest imaginable leak from a speedfit elbow joint on the hot water side . Theres a damp patch (oo - er ! there hasnt been one of these in my bedroom since my divorce !! - pls excuse my vulgarity ) underneath the calorifier which now makes sense as this leak iisnt big enough to cause a puddle as such but over time will / has create damp .

SO . do i -

1 isolate water to pump ... turn the tap

2 disconnect pump from 12 v supply

3 turn on hot tap to draw most of the water from the pipes between calorifier & tap in bathroom

4 disconnect problem speedfit elbow , inspect & replace

5 reconnect elbow & reverse the procedure & test

 

IF successful would this be the same process to follow when / if fitting an expansion tank as it would go onto the same pipe as the probkem speedfit elbow .

 

Once again my apologies to all for my simplistic descriptions ...... a plumber i am most definately not and again my gratitude fir your help ,

 

cheers

[chubby]

Hello .... again

 

One more thing to clarify before spending more cash . Blackrose mentions i need an expansion tank if theres a NRV between the pump and the cold inlet on the calorifier . Trackman , you say theres a NRV built into the calorifier itself .

Therefore i DO have an NRV even tho theres not one between my pump and calorifier on the existing pipework ?

This means therefore i WILL need an expansion tank . If so then i should fit the expansion tank and replace the problem elbow at the same time . If so im jumping on a bus to Uxbridge once ive called to see if they have one . I just hope if fits under my bed as thats the ONLY place it can go between the hot outlet & the first hot tap in the bathroom . The opinion seems to be the Screwfix tank is not suitable so I shall take it back .

 

cheers once more ...

[Dominic M]

Chubby - pretty much yes, although you don't need to disconnect the pump physically, just turn off the power to it. Drain any residual water you can mange too through the open taps, then get a big towel or even better, Tesco Value disposable nappies, under the weeping elbow joint before you disconnect it because unless you are very fortunate there will be water left in the pipework. Asa for your PRV weeping when the water is hot, that's not a problem, it's doing the job it's designed to do. It's just that the excess water should be plumbed out through an overflow pipe through the hull side of the boat (at least 10in above the water line) via a skin fitting. Although you've set the thermostat on your immersion, is the water extremely hot? If so, the immersion thermostat may need replacing.

[nicknorman]

Yes the most important thing is to depressurise the system before you start, by turning off the pump and turning on hot and cold taps. Its difficult to say without seeing your exact layout, but gravity is your friend and if you can open a tap / disconnect something over a bucket that is below the level of where you want to disconnect the pipework, that will minimise water loss. Have towels at hand as has been said.

 

On the subject of the weeping connection, these speedfit connections are usually pretty good but one source of problem is that poor cutting of the pipe can leave rough or scratched edges. The fitting seals by means of an O-ring around the outside of the pipe, if that area is not completely smooth a slight leak may occur. Therefore check visually for this, and of course check the fittings are fully pushed home with no dirt. Its also possible for the fitting to have cracked if it has frost damage.

 

Hello .... again

 

One more thing to clarify before spending more cash . Blackrose mentions i need an expansion tank if theres a NRV between the pump and the cold inlet on the calorifier . Trackman , you say theres a NRV built into the calorifier itself .

Therefore i DO have an NRV even tho theres not one between my pump and calorifier on the existing pipework ?

This means therefore i WILL need an expansion tank . If so then i should fit the expansion tank and replace the problem elbow at the same time . If so im jumping on a bus to Uxbridge once ive called to see if they have one . I just hope if fits under my bed as thats the ONLY place it can go between the hot outlet & the first hot tap in the bathroom . The opinion seems to be the Screwfix tank is not suitable so I shall take it back .

 

cheers once more ...

We have an NRV, an immersion heater and NO expansion tank. We accept that a small quantity of water will exit the PRV and its plumbed into the stern gland bilge, where the automatic bilge pump takes care of it. If you do this, an expansion vessel will not be necessary. If you don't do this, you will eventually have some water coming out of the PRV into the boat for whatever reason. Therefore, do it! (and forget the expansion vessel!)

[Alastair]

The other problem that can occur with speed fit is if someone has neglected to fit a ferrule in the pipe end. You have to pull the pipe out of the fitting to check this. It's just a little sleeve that slips in the end of the pipe.

[Captain Fizz]

Sound advice from Nicknorman. It is worth the money,(not expensive) to use the proper cutters for plastic pipe so that you get a clean cut without any scoring.

Fit a skin fitting for discharge and forget an expansion vessel.

Current thinking on Legionella is 20-45 celcius so you could turn down the thermostat some if you wish.

[chubby]

Cheers folks ,

 

Ok . Im unable to drain from the PRV to the engine area as there is a steel bulkhead between the bedroom & engine area . ( its a liverpool boats build if thats relevant ) So i m expecting to possibly fit an expansion tank and keep the PRV piped to a container just incase . Perhaps at a later date - next Spring for instance when i take the boat to a yard to be blacked , i could have a skin fitting added to make a permanent solution as a last resort should there be a problem .

In the meantime i need to sort my dripping PRV and elbow joint . Any cuts ive made in the speedfit pipe have been with the special cutter they recommend and ive used the inserts on the pipes so how this one elbow has leaked is , like all plumbing , a mystery .

So - im off to Uxbridge now . When i get back i shall follow the procedure i theorised about and which , thanks to your replies appears to be the way forward , to ensure minimal loss of water from the pipes and fit the expansion tank .

Then i shall need to get a tyre pressure gauge to make the necessary adjustments to the expansion tank . I have a large bicycle pump with pressure guage - is this suitable .. ish ?

 

cheers

[chubby]

hello again

 

Thankyou to everyone who has replied with help & suggestions - i am extremely grateful and its very uplifting to receive such a response from folk i dont even know so again , thankyou all .

 

Ive now fitted an 8 litre expansion tank and there was not much water loss from the pipes when i mustered up enough cojones to cut them ! I need to now make the adjustments in the pressure of the expansion tank to hopefully ensure it is working as efficiently as it can . I have no idea of my pumps cut in pressure ( shurflo ) and the manual appears to not have this info . On the side of the pump it says 30 psi . After the accumulator there is a

[bizzard]

To revive another old wheeze. A Champagne bottle with half blown up balloon inside with a straight nozzle or T piece Araldited into its neck.

[chubby]

sorry about that - i shall continue

 

after the accumulator theres a pressure refucing valve with a gauge set to 2 bar / 29 psi so i guess this is the max pressure that can flow from the accumulator to the calorifier .

So can anyone suggest a PSI that i should set the expansion tank to .

 

The flow actually seems quite weak at the taps so could / should i adjust the pressure reducing valve up to say 2.5 bar and then set the expansion tank according to this pressure instead in order to make the flow at the taps better ?

Blackrose suggested some figures in the first reply i got but these are relative to my pumps cut in pressure which i cannot determine

 

again thanks for any help - i feel like victory is not far away but .......

 

cheers

[nicknorman]

Firstly, don't forget its cut out pressure not cut in pressure. 30psi is probably right, but if you want to measure it here's how.

 

Put a modest pressure, say 20psi into the expansion vessel with the water system depressurised (pump off, hot tap open)

Close tap, turn on pump

Using a tyre pressure gauge, measure the new pressure in the expansion vessel. It will be the same as the pump cut-out pressure.

Turn off pump, open hot tap.

Now pump up the air pressure in the expansion vessel until it is the same as the previous measurement, or perhaps just a psi or two less.

Close tap, turn on pump

 

Robert is now your mother's brother.

 

Edited in the light of your second post:

 

Before deciding whether to remove the reducer, check the pressure of the PRV. It will hopefully be on a label on the PRV. The PRV needs to have a reasonable margin above the pump pressure in order that the expansion vessel can absorb the thermal expansion. There is no exact answer as it depends on too many things, but for example if the pump is 30psi/2bar and the PRV is 45psi/3bar that is likely to be OK.

 

Re-editing because if the pump is 30psi and the reducer is 2 bar ( I think that's what you said) they are the same thing, so no point in the reducer and it might be reducing the flow rate.

Edited October 22, 2013 by nicknorman

[chubby]

Hi

 

Thank nicknorman

 

ok im worried now that something is going very very wrong . my waterpump is now not working at all . it is completely dead and im totally lost as to why it has now packed up .

it looks like the wire to the pump are no longer working . i ve put a 12 v fan that i know works onto the wires and theres nothing . im really very worried now

Any suggestions please

 

thanks