Now here's a funny thing

Vicdicdoc

I finally got the water system up & running, I fitted J Guest 13(or is it 15mm) from the pump to a 'T' where it reduces to 10mm throughout except for the hot water side from that 'T' to the rear of the van (where the water heater is - 3m) back to 13/15mm J Guest piping, turning on the cold water sink tap or shower tap the pump cuts in & operates perfectly . . turn either tap to hot & the pump cycles on & off with a reduced flow compared to the cold water - I'm wondering if the cycling is due to the larger pipe bore not creating sufficient pump pressure (no leaks anywhere on the system) - What's your opinion causing this ?
 

fifthwheel

Could it be a restriction in the water heater? If it cycles on and off it must be building up pressure somewhere to do this. If no restriction I would have thought it would run continuously. john

PS. I know the flow is reduced but have you still got pressure?
 

Millie Master

Forum Member
The problem could be being caused by an air bubble in the system if there are any high points along its route. I had exactly the same problem only recently with my kitchen sink whereas the shower taps were working perfectly. However going up and down to such a very significant extent with the pipe sizes could well be causing the problem.......... my system is 10mm throughout.

Phil
 

Squiffy

Forum Member
What is your reason for the difference in pipe diameter? I have always used 10mm through out without a problem in hot or cold delivery. I think both answers given so far have merit in so much as if the pump cycles it must be building pressure in the hot system to turn the pump off and on. How much difference in flow/delivery is there. With the cold 10mm side the pump could very well be building enough pressure in the restricted 10mm pipe to stop the pump cycling, but in the 15mm side it is having to build up pressure time by by the equivalent of the extra 5mm square internal area so hence by the time the tap has delivered hot water the pressure has dropped enough to turn the pump back on where as with the cold tap it can deliver considerably more water that has been built up in the system before the pressure drops enough to turn the pump on.
Increasing the pump pressure might stop the pump recycling so much on the hot side
But it will in my opinion always cycle more on the hot side than on the cold. 🤔 Phil

P.s Also what do you consider normal operation.
 

Deleted member 4404

Like Phil, I would make sure there is no air trapped in the pipework or water heater
 

Vicdicdoc

Thanks for these replies, my thinking when laying in the pipes was 10mm on the ‘branch’ lines and larger dia pipe to the back of the van where the water heater is (which is 1metre higher than the pump) then back to 10mm on the delivery side of the water heater - (a) would increasing the pressure in the accumulator solve the problem? Or (b) should I replace the larger bore pipe with 10mm ? I’m assuming that the Shurflo pump has sufficient omph to overcome the 1metre height ?
 

Millie Master

Forum Member
I’m assuming that the Shurflo pump has sufficient omph to overcome the 1metre height ?

Although the Shurflo pumps are powerful, a 1 mtr., your lift height might be your problem if there are any glitches or weaknesses in the rest of the system and the fact that there isn't uniformity of size in the rest of your pipework that could all add up to the kind of problems you are experiencing Vic.
But, I could be very wrong and it might be only a hydraulics specialist who will be able to answer your problems.

Phil
 

Squiffy

Forum Member
I think that some of the big American RV's have at least a 1mtr height difference and I'm fairly certain I read somewhere over the years that Shureflo pumps are good for 3mtr head 🙄 but certainly 1 mtr should be no problem I would have thought. Phil

Thinking about it my shower head is at least 1.5 mtr above my pump and a good 2mtrs above the lowest part of my water tank.
 

fifthwheel

I finally got the water system up & running, I fitted J Guest 13(or is it 15mm) from the pump to a 'T' where it reduces to 10mm throughout except for the hot water side from that 'T' to the rear of the van (where the water heater is - 3m) back to 13/15mm J Guest piping, turning on the cold water sink tap or shower tap the pump cuts in & operates perfectly . . turn either tap to hot & the pump cycles on & off with a reduced flow compared to the cold water - I'm wondering if the cycling is due to the larger pipe bore not creating sufficient pump pressure (no leaks anywhere on the system) - What's your opinion causing this ?
If I am reading this correctly when a hot tap is opened your pump starts then cycles as water is being delivered. This would indicate a restriction somewhere heater/accumulator? Can you disconnect the output from the pump and then the accumulator to check the flow and pressure?
 

Vicdicdoc

I think I’ll replace the larger bore pipe with 10mm (access not too difficult as I’ve not finished laying the floor) & then see if the pump cycling is cured
 

fifthwheel

I think I’ll replace the larger bore pipe with 10mm (access not too difficult as I’ve not finished laying the floor) & then see if the pump cycling is cured
I think I’ll replace the larger bore pipe with 10mm (access not too difficult as I’ve not finished laying the floor) & then see if the pump cycling is cured
If the accumulator is adjustable it might be set too high, easier to check first before replace pipework.
 

Vicdicdoc

I was thinking that too, nothing lost if I try both reducing the accumulator pressure and or increasing the pressure
 

Vicdicdoc

Van has been back in storage over Easter and I’ll go get it later- Grrr we’ve missed getting out during this lovely weather ho hum
 

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